Monovalent, bivalent and trivalent anti human respiratory syncytial virus (HRSV) nanobody constructs for the prevention and/or treatment of respiratory tract infections

ABSTRACT

Amino acid sequences are provided that are directed against and/or that can specifically bind protein F of hRSV, as well as to compounds or constructs, and in particular proteins and polypeptides, that comprise or essentially consist of one or more such amino acid sequences. The amino acid sequences, polypeptides and therapeutic compounds and compositions provided by the invention show an improved stability, less immunogenicity and/or improved affinity and/or avidity for protein F of hRSV. The invention also relates to the uses of such amino acid sequences, polypeptides, compounds or constructs for prophylactic and/or therapeutic purposes.

RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. §371 ofinternational application PCT/EP2010/057921, filed Jun. 7, 2010, whichwas published under PCT Article 21(2) in English, and claims the benefitunder 35 U.S.C. §119(e) of U.S. provisional application Ser. No.61/184,396, filed Jun. 5, 2009, and U.S. provisional application Ser.No. 61/265,014, filed Nov. 30, 2009, the disclosures of which areincorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates to amino acid sequences that are directedagainst/and or that can specifically bind (as defined herein) protein Fof hRSV, as well as to compounds or constructs, and in particularproteins and polypeptides, that comprise or essentially consist of oneor more such amino acid sequences (also referred to herein as “aminoacid sequence(s) of the invention”, “compound(s) of the invention”,“construct(s) of the invention” and “polypeptide(s) of the invention”,respectively).

The invention also relates to nucleic acids encoding such amino acidsequences and polypeptides (also referred to herein as “nucleic acid(s)of the invention” or “nucleotide sequence(s) of the invention”); tomethods for preparing such amino acid sequences and polypeptides; tohost cells expressing or capable of expressing such amino acid sequencesor polypeptides; to compositions, and in particular to pharmaceuticalcompositions, that comprise such amino acid sequences, polypeptides,compounds or constructs, nucleic acids and/or host cells; and to uses ofsuch amino acid sequences, polypeptides, compounds or constructs,nucleic acids, host cells and/or compositions, in particular forprophylactic and/or therapeutic purposes, such as the prophylacticand/or therapeutic purposes mentioned herein.

Other aspects, embodiments, advantages and applications of the inventionwill become clear from the further description herein.

BACKGROUND ART

Human respiratory syncytial virus (hRSV) is a member of theParamyxoviridae family and is an enveloped virus with two main surfaceglycoproteins that make the spikes of the virus particle. One of theseglycoproteins (protein G) is the attachment protein that mediatesbinding of the virus to the cell surface. The other glycoprotein(protein F or fusion) mediates fusion of the viral and cell membranes,allowing the entry of the viral nucleocapsid into the cell cytoplasm.Inhibition of the steps mediated by either G or F glycoproteins blocksthe initial stages of the infectious cycle and neutralizes virusinfectivity. Therefore, antibodies directed against either G or F, andwhich inhibit their respective activities, may neutralize virusinfectivity and may protect against a hRSV infection. The F protein ishighly conserved and forms trimeric spikes that undergo conformationalchanges upon activation.

hRSV is the leading cause of severe lower respiratory tract infections(bronchiolitis and pneumonia) in infants and very young children andcauses annual epidemics during the winter months. The virus also causesa substantial disease burden among the elderly and adults withunderlying cardiopulmonary disorders and/or immunosuppressive conditionsare also at risk of severe hRSV disease. The immune response does notprevent re-infections.

There is no vaccine available to prevent hRSV infections. The only drugproduct available in the market is a humanized monoclonal antibody(Synagis®) directed against one of the viral glycoproteins (protein F)which is used prophylactically in children that are at a very high riskof suffering a severe hRSV infection. The restricted use of Synagis® isdue, at least in part, to the high cost of this product. There isclearly a need for improved and/or cheaper prophylactic and/ortherapeutic agents for the prevention and or treatment of infections byhRSV.

SUMMARY OF THE INVENTION

The present invention provides amino acid sequences (also referred to as“amino acid sequence(s) of the invention”), polypeptides (also referredto as “polypeptide(s) of the invention”) and therapeutic compounds andcompositions that are directed against protein F of hRSV and that haveimproved prophylactic, therapeutic and/or pharmacological properties, inaddition to other advantageous properties (such as, for example,improved ease of preparation and/or reduced costs of goods), compared tothe prior art amino acid sequences and antibodies. These improved andadvantageous properties will become clear from the further descriptionherein. Without being limiting, the amino acid sequences, polypeptidesand therapeutic compounds and compositions provided by the invention mayshow an improved stability, less immunogenicity, improved binding toprotein F of hRSV, improved affinity and/or avidity for protein F ofhRSV, improved efficacy and/or potency for neutralizing hRSV (as definedherein), an increased selectivity for protein F of hRSV and/or they maybe capable of partially or preferably totally blocking the interactionof protein F of hRSV with the target host cell and/or its membrane. Theymay be capable of neutralizing hRSV by modulating, inhibiting and/orpreventing hRSV infectivity, by modulating, inhibiting and/or preventinghRSV fusion with (the cell membrane of) the target host cell, and/or bymodulating, inhibiting and/or prevent hRSV entry in the target host cell(as defined herein). They may be cross reactive with and/or capable ofneutralizing different strains of hRSV and/or different hRSV escapemutants.

In a first aspect, the present invention provides a number of stretchesof amino acid residues (as defined herein) that are particularly suitedfor binding to a specific epitope on protein F of hRSV. These stretchesof amino acid residues may be present in, and/or may be incorporatedinto, an amino acid sequence of the invention, in particular in such away that they form (part of) the antigen binding site of the amino acidsequence of the invention. The resulting amino acid sequences will becapable of binding a specific epitope on protein F of hRSV that lies in,forms part of, or overlaps with (i.e. in the primary or tertiarystructure) or is in close proximity to (i.e. in the primary or tertiarystructure) antigenic site II on protein F of hRSV (i.e. amino acidresidues 250-275 of protein F of hRSV).

Accordingly, in one aspect, the present invention provides amino acidsequences that comprise at least a stretch of amino acid residues chosenfrom the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

In a preferred aspect, the present invention provides amino acidsequences that comprise two or more stretches of amino acid residues inwhich one stretch is chosen from the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a), and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).

Even more preferably, the amino acid sequences of the invention comprisethree or more stretches of amino acid residues, in which the firststretch of amino acid residues is chosen from the group consisting of:

-   -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference; or        the second stretch of amino acid residues is chosen from the        group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;            and the third stretch of amino acid residues is chosen from            the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Amino acid sequences comprising one or more of these specific stretchesof amino acid residues have shown improved properties such as e.g.improved binding characteristics (suitably measured and/or expressed asa K_(D)-value (actual or apparent), a K_(A)-value (actual or apparent),a k_(on)-rate and/or a k_(off)-rate, or alternatively as an IC₅₀ value,as further described herein), improved affinity and/or improved avidityfor protein F of hRSV and/or improved efficacy and/or potency forneutralizing hRSV.

The amino acid sequence of the invention may in particular be a domainantibody (or an amino acid sequence that is suitable for use as a domainantibody), a single domain antibody (or an amino acid sequence that issuitable for use as a single domain antibody), a “dAb” (or an amino acidsequence that is suitable for use as a dAb) or a Nanobody® (as definedherein, and including but not limited to a V_(HH) sequence); othersingle variable domains, or any suitable fragment of any one thereof.

In this respect, the amino acid sequences of the invention mayessentially consist of 4 framework regions (FR1 to FR4, respectively)and 3 complementarity determining regions (CDR1 to CDR3, respectively),in which CDR2 is chosen from:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

These preferred complementarity determining regions (CDR2 sequences) arealso referred to as “CDR2(s) of the invention”.

Preferably, the amino acid sequences of the invention may essentiallyconsist of 4 framework regions (FR1 to FR4, respectively) and 3complementarity determining regions (CDR1 to CDR3, respectively), inwhich CDR2 is chosen from the group consisting of:

-   -   a) SEQ ID NO: 102; or    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one of CDR1 or CDR3 is chosen from:        -   CDR1 chosen from the group consisting of:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference; or    -   and/or        -   CDR3 chosen from the group consisting of:    -   e) SEQ ID NO: 121; or    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Even more preferably, the amino acid sequences of the invention mayessentially consist of 4 framework regions (FR1 to FR4, respectively)and 3 complementarity determining regions (CDR1 to CDR3, respectively),in which:

-   -   CDR1 is chosen from the group consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and        -   CDR2 is chosen from the group consisting of:    -   c) SEQ ID NO: 102; or    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and        -   CDR3 is chosen from the group consisting of:        -   e) SEQ ID NO: 121;        -   f) a stretch of amino acid residues that has no more than 3,            preferably no more than 2, more preferably no more than 1            amino acid difference with SEQ ID NO: 121, provided that the            amino acid sequence comprising said stretch of amino acid            residues binds protein F of hRSV with the same, about the            same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

In a specific aspect, the amino acid sequence or Nanobody® of theinvention comprises at least SEQ ID NO: 102. Preferably, the amino acidsequence or Nanobody® of the invention comprises SEQ ID NO: 98, SEQ IDNO: 102 and SEQ ID NO: 121.

The present invention also provides a number humanized amino acidsequences that are particularly suited for binding protein F of hRSV.The amino acid sequences of the present invention show reducedimmunogenicity upon administration to a human subject. In addition, theamino acid sequences of the present invention show other improvedproperties such as e.g. improved binding characteristics (suitablymeasured and/or expressed as a K_(D)-value (actual or apparent), aK_(A)-value (actual or apparent), a k_(on)-rate and/or a k_(off)-rate,or alternatively as an IC₅₀ value, as further described herein) forprotein F of hRSV, improved affinity and/or improved avidity for proteinF of hRSV and/or improved efficacy and/or potency for neutralizing hRSVcompared to their corresponding wild type amino acid sequences (asdescribed in PCT application PCT/EP2009/056975 entitled “Amino acidsequences directed against envelope proteins of a virus and polypeptidescomprising the same for the treatment of viral diseases” filed by AblynxN. V on 5 Jun. 2009).

Accordingly, in another aspect, the present invention provides aminoacid sequences chosen from the following:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence of the inventioncomprises or essentially consists of SEQ ID NO: 60-76.

In another aspect, the present invention provides amino acid sequenceschosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences of the invention comprise or essentiallyconsists of one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76.

In yet another aspect, the present invention provides amino acidsequences chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence of the inventioncomprises or essentially consists of SEQ ID NO: 65. In another preferredaspect, the amino acid sequence of the invention comprises oressentially consists of SEQ ID NO: 76.

In another aspect, the present invention provides amino acid sequenceschosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence of the inventioncomprises or essentially consists of SEQ ID NO: 146-153.

In another aspect, the present invention provides amino acid sequenceschosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences of the invention comprise or essentiallyconsist of one of SEQ ID NO's: 146-149 and 151-153.

The present invention provides a number of sequence optimized amino acidsequences and/or Nanobodies® that show increased stability upon storageduring stability studies and that are particularly suited for bindingprotein F of hRSV. The amino add sequences of the present invention showreduced pyroglutamate post-translational modification of the N-terminusand hence have increased product stability. In addition, the amino acidsequences of the present invention show other improved properties suchas e.g. less immunogenicity, improved binding characteristics (suitablymeasured and/or expressed as a K_(D)-value (actual or apparent), aK_(A)-value (actual or apparent), a k_(on)-rate and/or a k_(off)-rate,or alternatively as an IC₅₀ value, as further described herein) forprotein F of hRSV, improved affinity and/or improved avidity for proteinF of hRSV and/or improved efficacy and/or potency for neutralizing hRSVcompared to their corresponding parental amino acid sequences (asdescribed in PCT application PCT/EP2009/056975 entitled “Amino acidsequences directed against envelope proteins of a virus and polypeptidescomprising the same for the treatment of viral diseases” filed by AblynxN. V on 5 Jun. 2009).

Accordingly, in one aspect of the present invention, amino acidsequences and/or Nanobodies® are provided chosen from the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence and/or Nanobody® of theinvention comprises or essentially consists of one of SEQ ID NO's:138-141 and 154-157.

The amino acid sequences and Nanobodies® provided by the invention arepreferably in essentially isolated form (as defined herein), or formpart of a protein or polypeptide of the invention (also referred to as“polypeptide of the invention” or “protein of the invention”), which maycomprise or essentially consist of one or more amino acid sequences orNanobodies® of the invention and which may optionally further compriseone or more further amino acid sequences or Nanobodies® (all optionallylinked via one or more suitable linkers).

Accordingly, in another aspect, the invention also relates to a proteinor polypeptide (also referred to herein as a “polypeptide of theinvention”, respectively) that comprises or essentially consists of oneor more amino acid sequences and/or Nanobodies® of the invention (orsuitable fragments thereof)

For example, and without limitation, the one or more amino acidsequences and/or Nanobodies® of the invention may be used as a bindingunit in such a protein or polypeptide, so as to provide a monovalent,multivalent or multiparatopic polypeptide of the invention,respectively, all as described herein. The present invention thus alsorelates to a polypeptide which is a monovalent construct comprising oressentially consisting of an amino acid sequence or a Nanobody® of theinvention. The present invention thus also relates to a polypeptidewhich is a multivalent polypeptide, such as e.g. a bivalent or trivalentpolypeptide. The present invention also relates to a polypeptide whichis a multiparatopic polypeptide, such as e.g. a bisparatopic ortriparatopic polypeptide.

In a preferred aspect, the invention provides a multivalent, preferablya bivalent or trivalent polypeptide comprising or essentially consistingof at least two amino acid sequences and/or Nanobodies® of the invention(as described above).

In one aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) or at least three (preferablyidentical) amino acid sequences or Nanobodies® chosen from amino acidsequences that comprise at least a stretch of amino acid residues chosenfrom the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) or at least three (preferablyidentical) amino acid sequences or Nanobodies® chosen from amino acidsequences that comprise two or more stretches of amino acid residues inwhich one stretch is chosen from the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino add sequence comprising said stretch            of amino add residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a), and b) should always be present in the amino acid        sequence that forms part of the multivalent polypeptide and such        that the second stretch of amino acid residues is chosen from        one of c), d), e) and f).

Preferred multivalent (such as bivalent or trivalent) polypeptides maycomprise or essentially consist of at least two (preferably identical)or at least three (preferably identical) amino acid sequences orNanobodies® chosen from amino acid sequences that comprise three or morestretches of amino acid residues, in which the first stretch of aminoacid residues is chosen from the group consisting of:

-   -   a) SEQ ID NO: 98;    -   b) a stretch of amino add residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference; or        the second stretch of amino acid residues is chosen from the        group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;            and the third stretch of amino acid residues is chosen from            the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Multivalent (such as bivalent or trivalent) polypeptides may comprise oressentially consist of at least two (preferably identical) or at leastthree (preferably identical) amino acid sequences or Nanobodies® thatessentially consist of 4 framework regions (FR1 to FR4, respectively)and 3 complementarity determining regions (CDR1 to CDR3, respectively),in which CDR2 is chosen from:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

Multivalent (such as bivalent or trivalent) polypeptides may comprise oressentially consist of at least two (preferably identical) or at leastthree (preferably identical) amino acid sequences or Nanobodies® thatessentially consist of 4 framework regions (FR1 to FR4, respectively)and 3 complementarity determining regions (CDR1 to CDR3, respectively),in which CDR2 is chosen from the group consisting of:

-   -   a) SEQ ID NO: 102; or    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one of CDR1 or CDR3 is chosen from:        -   CDR1 chosen from the group consisting of:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference; or    -   and/or        -   CDR3 chosen from the group consisting of:    -   e) SEQ ID NO: 121; or    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Preferably, multivalent (such as bivalent or trivalent) polypeptides maycomprise or essentially consist of at least two (preferably identical)or at least three (preferably identical) amino acid sequences orNanobodies® that essentially consist of 4 framework regions (FR1 to FR4,respectively) and 3 complementarity determining regions (CDR1 to CDR3,respectively), in which:

-   -    CDR1 is chosen from the group consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and        -   CDR2 is chosen from the group consisting of:    -   c) SEQ ID NO: 102; or    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and        -   CDR3 is chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

In a specific aspect, the multivalent (such as bivalent or trivalent)polypeptides may comprise or essentially consist of at least two(preferably identical) or at least three (preferably identical) aminoacid sequences or Nanobodies® that comprise at least SEQ ID NO: 102,preferably that comprise SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO:121.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 60-76.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 62, 65,67, 68, 75 and 76.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, at position 78 and/or an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 65 and76.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 60-76.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 62, 65,67, 68, 75 and 76.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 65 and76.

A preferred multivalent polypeptide of the invention comprises oressentially consists of three amino acid sequences or Nanobodies® withSEQ ID NO: 62. Another preferred multivalent polypeptide of theinvention comprises or essentially consists of three amino acidsequences or Nanobodies® with SEQ ID NO: 65. Another preferredmultivalent polypeptide of the invention comprises or essentiallyconsists of three amino acid sequences or Nanobodies® with SEQ ID NO:76.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 146-153.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 146-149and 151-153.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 146-153.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic add (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic add (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from the group consisting of SEQ ID NO's: 146-149and 151-153.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least one amino acid sequence or Nanobody® chosen from thefollowing:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least one amino acid sequence or Nanobody®chosen from the group consisting of SEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least one amino acid sequence or Nanobody® chosen from thefollowing:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is atrivalent polypeptide that comprises or essentially consists of at leastone amino acid sequence or Nanobody chosen from the group consisting ofSEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 77-79 and 158;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 77-79 and 158, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Glutamine (Gln, Q) at position 105, a            Leucine (Leu, L) at position 78, an Arginine (Arg, R) at            position 83 and/or a Glutamic acid (Glu, E) at position 85            (said positions determined according to Kabat numbering);            and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of one of SEQ ID NO's: 77-79 and 158.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 78 and 79;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 78 and 79, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has an Aspartic acid (Asp, D) at position 54, a            Glutamine (Gln, Q) at position 105, a Leucine (Leu, L) at            position 78, an Arginine (Arg, R) at position 83 and/or a            Glutamic acid (Glu, E) at position 85 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of SEQ ID NO: 78 or 79.

In another specific aspect, the polypeptide of the invention essentiallyconsists of the amino acid sequence of SEQ ID NO: 77. In anotherspecific aspect, the polypeptide of the invention essentially consistsof the amino acid sequence of SEQ ID NO: 78. In another specific aspect,the polypeptide of the invention essentially consists of the amino acidsequence of SEQ ID NO: 79. In another specific aspect, the polypeptideof the invention essentially consists of the amino acid sequence of SEQID NO: 158.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Proline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20 and            Leucine (Leu, L) at position 108 (said positions determined            according to Kabat numbering); and        -   iii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the amino acid            sequence without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of one of SEQ ID NO's: 159-161.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Praline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20 and            Leucine (Leu, L) at position 108 and in addition Arginine            (Arg, R) at position 83, Glutamic acid (Glu, E) at position            85 and/or Glutamine (Gln, Q) at position 105 so that when            the polypeptide has no more than 3, preferably no more than            2, more preferably no more than 1 amino acid difference            with:            -   SEQ ID NO: 159, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83 and Glutamine (Gln, Q) at                position 105;            -   SEQ ID NO: 160, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83, Glutamic acid (Glu, E) at                position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 161, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83 and Glutamic acid (Glu, E) at                position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the amino acid            sequence without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of SEQ ID NO: 159-161.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 142-145 and 162-165;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NQ's: 142-145 and 162-165, provided that:        -   i) the first amino acid sequence or Nanobody® encompassed in            said polypeptide has an Aspartic acid (Asp, D) at position 1            (said position determined according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of one of SEQ ID NO's: 142-145 and 162-165.

Polypeptides with these sequences show advantageous properties for useas prophylactic, therapeutic and/or pharmacologically active agents suchas e.g. improved stability, less immunogenicity, improved bindingcharacteristics (suitably measured and/or expressed as a K_(D)-value(actual or apparent), a K_(A)-value (actual or apparent), a k_(on)-rateand/or a k_(off)-rate, or alternatively as an IC₅₀ value, as furtherdescribed herein), improved affinity and/or improved avidity for proteinF of hRSV and/or improved efficacy and/or potency for neutralizing hRSV.

The invention further relates to compounds or constructs, and inparticular proteins or polypeptides (also referred to herein as a“compound(s) of the invention”) that comprise or essentially consist ofone or more amino acid sequences, Nanobodies® and/or polypeptides of theinvention (or suitable fragments thereof), and optionally furthercomprise one or more other groups, residues, moieties or binding units.As will become clear to the skilled person from the further disclosureherein, such further groups, residues, moieties, binding units or aminoacid sequences may or may not provide further functionality to the aminoacid sequence, Nanobody® or polypeptide of the invention (and/or to thecompound or construct in which it is present) and may or may not modifythe properties of the amino acid sequence, Nanobody® and/or polypeptideof the invention.

It is also within the scope of the invention to use parts, fragments,analogs, mutants, variants, alleles and/or derivatives of the amino acidsequences and/or polypeptides of the invention, and/or to use proteinsor polypeptides comprising or essentially consisting of one or more ofsuch parts, fragments, analogs, mutants, variants, alleles and/orderivatives, as long as these are suitable for the uses envisagedherein. Such parts, fragments, analogs, mutants, variants, allelesand/or derivatives will usually contain (at least part of) a functionalantigen-binding site for binding against antigenic site II on protein Fof hRSV; and more preferably will be capable of specific binding toantigenic site II on protein F of hRSV, and even more preferably capableof binding to antigenic site II on protein F of hRSV with an affinity(suitably measured and/or expressed as a K_(D)-value (actual orapparent), a K_(A)-value (actual or apparent), a k_(on)-rate and/or ak_(off)-rate, or alternatively as an IC₅₀ value, as further describedherein) that is as defined herein. Such parts, fragments, analogs,mutants, variants, alleles and/or derivatives will usually also have ahRSV neutralization efficacy and/or potency as defined herein. Somenon-limiting examples of such parts, fragments, analogs, mutants,variants, alleles, derivatives, proteins and/or polypeptides will becomeclear from the further description herein. Additional fragments orpolypeptides of the invention may also be provided by suitably combining(i.e. by linking or genetic fusion) one or more (smaller) parts orfragments as described herein.

The invention also relates to nucleic acids or nucleotide sequences thatencode an amino acid sequence of the invention, a Nanobody® of theinvention and/or a polypeptide of the invention (or a suitable fragmentthereof). Such a nucleic acid will also be referred to herein as“nucleic acid(s) of the invention” and may for example be in the form ofa genetic construct, as further described herein. Accordingly, thepresent invention also relates to a nucleic acid or nucleotide sequencethat is in the form of a genetic construct.

The invention further relates to a host or host cell that expresses (orthat under suitable circumstances is capable of expressing) an aminoacid sequence of the invention, a Nanobody® of the invention, apolypeptide of the invention and/or a compound or construct of theinvention; and/or that contains a nucleic acid of the invention. Somepreferred but non-limiting examples of such hosts or host cells willbecome clear from the further description herein.

The invention further relates to a product or composition containing orcomprising at least one amino acid sequence of the invention (or asuitable fragment thereof), at least one Nanobody® of the invention, atleast one polypeptide of the invention, at least one compound orconstruct of the invention, at least one monovalent construct of theinvention and/or at least one nucleic acid of the invention, andoptionally one or more further components of such compositions known perse, i.e. depending on the intended use of the composition. Such aproduct or composition may for example be a pharmaceutical composition(as described herein) or a veterinary composition. Some preferred butnon-limiting examples of such products or compositions will become clearfrom the further description herein.

The invention further relates to methods for preparing the amino acidsequences, Nanobodies®, polypeptides, nucleic acids, host cells,products and compositions described herein.

The invention further relates to applications and uses of the amino acidsequences, Nanobodies®, polypeptides, compounds, nucleic acids, hostcells, products and compositions described herein, as well as to methodsfor the prevention and/or treatment of respiratory track infectioncaused by hRSV. Some preferred but non-limiting applications and useswill become clear from the further description herein.

The amino acid sequences, Nanobodies®, polypeptides, compounds andcompositions of the present invention can generally be used to block theinteraction of protein F of hRSV with the target host cell and/or itsmembrane, to neutralize hRSV (different hRSV strains and/or escapemutants), to modulate, inhibit and/or prevent hRSV infectivity (ofdifferent hRSV strains and/or escape mutants), to modulate, inhibitand/or prevent fusion (of different hRSV strains and/or escape mutants)with (the cell membrane of) the target host cell and/or to modulate,inhibit and/or prevent hRSV entry in the target host cell (of differenthRSV strains and/or escape mutants).

As such, the amino acid sequences, Nanobodies®, polypeptides, compoundsand compositions of the present invention can be used for the preventionand/or treatment of diseases and disorders associated with hRSVinfection. Examples of such diseases and disorders associated with hRSVinfection will be clear to the skilled person based on the disclosureherein, and for example include the following diseases and disorders:respiratory illness, upper respiratory tract infection, lowerrespiratory tract infection, bronchiolitis (inflammation of the smallairways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezingand asthma.

Accordingly, the present invention also relates to a method for theprevention and/or treatment of respiratory illness, upper respiratorytract infection, lower respiratory tract infection, bronchiolitis(inflammation of the small airways in the lung), pneumonia, dyspnea,cough, (recurrent) wheezing and/or asthma caused by hRSV, said methodcomprising administering, to a subject in need thereof, apharmaceutically active amount of at least one amino acid sequence ofthe invention, Nanobody® of the invention, polypeptide of the invention,compound or construct of the invention or monovalent construct of theinvention, or a composition of the invention.

The invention also relates to the use of an amino acid sequence of theinvention, a Nanobody® of the invention, a polypeptide of the invention,a compound or construct of the invention or a monovalent construct ofthe invention in the preparation of a pharmaceutical composition for theprevention and/or treatment of respiratory illness, upper respiratorytract infection, lower respiratory tract infection, bronchiolitis(inflammation of the small airways in the lung), pneumonia, dyspnea,cough, (recurrent) wheezing and/or asthma; and/or for use in one or moreof the methods described herein.

The invention also relates to an amino acid sequence of the invention, aNanobody® of the invention, a polypeptide of the invention, a compoundor construct of the invention or monovalent construct of the inventionfor prevention and/or treatment of respiratory illness, upperrespiratory tract infection, lower respiratory tract infection,bronchiolitis (inflammation of the small airways in the lung),pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma.

Other applications and uses of the amino acid sequences, Nanobodies®,polypeptides and compounds and compositions of the invention will becomeclear to the skilled person from the further disclosure herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: Competition ELISA: Synagis® Fab competes with purified RSVbinding Nanobodies® and Numax Fab for binding to F_(TM)-protein asdescribed in Example 8. Nanobody® 202A5 is an irrelevant Nanobody®binding HA of influenza.

FIG. 2: Binding of monovalent, bivalent and trivalent Nanobodies® toF_(TM)-protein as described in Example 10.

FIGS. 3A and B: Potency (RSV neutralization) of monovalent, bivalent andtrivalent constructs to neutralize Long and B-1 RSV strains as describedin Example 11.

FIG. 4: Neutralization assay of RSV Long and the escape mutants R7C2/1;R7C2/11 and R7.936/4 by the monovalent Nanobodies® 7B2 (A), 15H8, (B)NC41 (C) at a concentration range from about 2 μM to 6 nM and thetrivalent Nanobodies® RSV 400 (D), RSV 404 (E), RSV 407 (F) and RSV 403(G) at a concentration range of about 20 nM to 100 pM. Curve fitting wasonly done for data of monovalent Nanobodies®.

FIG. 5: Neutralization of RSV Long and RSV B-1 strains by trivalent NC41Nanobody® with different linker lengths as described in Example 15.

FIG. 6: Schematic overview of the humanized residues introduced inselected NC41 variants. Dots indicate the presence of the wildtyperesidue; letters correspond to the humanized residue. Numbering isaccording to Kabat.

FIG. 7: Alignment of preferred humanized Nanobody® sequences of theinvention.

FIG. 8: Neutralization of hRSV Long strain and B-1 strain by monovalentand trivalent humanized NC41 variants. In FIG. 8A, neutralization by twoof the trivalent humanized NC41 variants (RSV414 and RSV426) is comparedwith their corresponding monovalent Nanobodies®. FIG. 8B shows theneutralization by the trivalent NC41 variants (RSV414, RSV426 andRSV427).

FIG. 9: Neutralization of hRSV Long (A) and B-1 (B) strains by RSV407and RSV434.

FIG. 10: Efficacy testing (prophylactic) of RSV407 in cotton rat modelas described in Example 21. Rats were intranasally administered withvarious concentrations of RSV407 (day −1) 24 hours prior to RSVinfection (day 0). The virus titer (left, mean±sem, n=6) and viral RNAlevel (right) was determined in lung lavages at the peak level ofviremia, being day 4 after infection (*=P<0.05 in two tailed student'st-test versus untreated).

FIG. 11: Efficacy testing (therapeutic) of RSV434 in cotton rat model asdescribed in Example 21. Rats were infected with RSV on day 0 andtreated with 0, 1, 2, 4 or 20 mg/kg of RSV434 at day 2 and 3 byintranasal instillation (n=6). The virus titer in nasal (A) and lunglavages (B) was determined at the peak level of viremia (day 4 afterinfection). The horizontal lines show the detection limits.

DETAILED DESCRIPTION OF THE INVENTION

In the present description, examples and claims:

-   a) Unless indicated or defined otherwise, all terms used have their    usual meaning in the art, which will be clear to the skilled person.    Reference is for example made to the standard handbooks mentioned in    paragraph a) on page 46 of WO 08/020,079.-   b) Unless indicated otherwise, the terms “immunoglobulin sequence”,    “sequence”, “nucleotide sequence” and “nucleic acid” are as    described in paragraph b) on page 46 of WO 08/020,079.-   c) Unless indicated otherwise, all methods, steps, techniques and    manipulations that are not specifically described in detail can be    performed and have been performed in a manner known per se, as will    be clear to the skilled person. Reference is for example again made    to the standard handbooks and the general background art mentioned    herein and to the further references cited therein; as well as to    for example the following reviews Presta, Adv. Drug Deliv. Rev.    2006, 58 (5-6): 640-56; Levin and Weiss, Mol. Biosyst. 2006, 2(1):    49-57; Irving et al., J. Immunol. Methods, 2001, 248(1-2), 31-45;    Schmitz et al., Placenta, 2000, 21 Suppl. A, S106-12, Gonzales et    al., Tumour Biol., 2005, 26(1), 31-43, which describe techniques for    protein engineering, such as affinity maturation and other    techniques for improving the specificity and other desired    properties of proteins such as immunoglobulins.-   d) Amino acid residues will be indicated according to the standard    three-letter or one-letter amino acid code. Reference is made to    Table R-2 on page 48 of WO 08/020,079.-   e) When a nucleotide sequence or amino acid sequence is said to    “comprise” another nucleotide sequence or amino acid sequence,    respectively, or to “essentially consist of” another nucleotide    sequence or amino acid sequence, this has the meaning given in    paragraph i) on pages 51-52 of WO 08/020,079.-   f) The term “in essentially isolated form” has the meaning given to    it in paragraph j) on pages 52 and 53 of WO 08/020,079.-   g) The terms “domain” and “binding domain” have the meanings given    to it in paragraph k) on page 53 of WO 08/020,079.-   h) The terms “antigenic determinant” and “epitope”, which may also    be used interchangeably herein, have the meanings given to it in    paragraph 1) on page 53 of WO 08/020,079.-   i) As further described in paragraph m) on page 53 of WO 08/020,079,    an amino acid sequence (such as a Nanobody®, an antibody, a    polypeptide of the invention, or generally an antigen binding    protein or polypeptide or a fragment thereof) that can    (specifically) bind to, that has affinity for and/or that has    specificity for a specific antigenic determinant, epitope, antigen    or protein (or for at least one part, fragment or epitope thereof)    is said to be “against” or “directed against” said antigenic    determinant, epitope, antigen or protein.-   j) The term “specificity” has the meaning given to it in    paragraph n) on pages 53-56 of WO 08/020,079; and as mentioned    therein refers to the number of different types of antigens or    antigenic determinants to which a particular antigen-binding    molecule or antigen-binding protein (such as a Nanobody® or a    polypeptide of the invention) molecule can bind. The specificity of    an antigen-binding protein can be determined based on affinity    and/or avidity, as described on pages 53-56 of WO 08/020,079    (incorporated herein by reference), which also describes some    preferred techniques for measuring binding between an    antigen-binding molecule (such as a Nanobody® or polypeptide of the    invention) and the pertinent antigen. Typically, antigen-binding    proteins (such as the amino acid sequences, Nanobodies® and/or    polypeptides of the invention) will bind to their antigen with a    dissociation constant (K_(D)) of 10⁻⁵ to 10⁻¹² moles/liter or less,    and preferably 10⁻⁷ to 10⁻¹² moles/liter or less and more preferably    10⁻⁸ to 10⁻¹² moles/liter (i.e. with an association constant (K_(A))    of 10⁵ to 10¹² liter/moles or more, and preferably 10⁷ to 10¹²    liter/moles or more and more preferably 10⁸ to 10¹² liter/moles).    Any K_(D) value greater than 10⁴ mol/liter (or any K_(A) value lower    than 10⁴ M⁻¹) liters/mol is generally considered to indicate    non-specific binding. Preferably, a monovalent immunoglobulin    sequence of the invention will bind to the desired antigen with an    affinity less than 500 nM, preferably less than 200 nM, more    preferably less than 10 nM, such as e.g. between 10 and 5 nM.    Specific binding of an antigen-binding protein to an antigen or    antigenic determinant can be determined in any suitable manner known    per se, including, for example, Scatchard analysis and/or    competitive binding assays, such as radioimmunoassays (RIA), enzyme    immunoassays (EIA) and sandwich competition assays, and the    different variants thereof known per se in the art; as well as the    other techniques mentioned herein. As will be clear to the skilled    person, and as described on pages 53-56 of WO 08/020,079, the    dissociation constant may be the actual or apparent dissociation    constant. Methods for determining the dissociation constant will be    clear to the skilled person, and for example include the techniques    mentioned on pages 53-56 of WO 08/020,079.-   k) The half-life of an amino acid sequence, compound or polypeptide    of the invention can generally be defined as described in    paragraph o) on page 57 of WO 08/020,079 and as mentioned therein    refers to the time taken for the serum concentration of the amino    acid sequence, compound or polypeptide to be reduced by 50%, in    vivo, for example due to degradation of the amino acid sequence,    compound or polypeptide and/or clearance or sequestration of the    amino acid sequence, compound or polypeptide by natural mechanisms.    The in vivo half-life of an amino acid sequence, compound or    polypeptide of the invention can be determined in any manner known    per se, such as by pharmacokinetic analysis. Suitable techniques    will be clear to the person skilled in the art, and may for example    generally be as described in paragraph o) on page 57 of WO    08/020,079. As also mentioned in paragraph o) on page 57 of WO    08/020,079, the half-life can be expressed using parameters such as    the t1/2-alpha, t1/2-beta and the area under the curve (AUC).    Reference is for example made to the Experimental Part below, as    well as to the standard handbooks, such as Kenneth, A et al:    Chemical Stability of Pharmaceuticals: A Handbook for Pharmacists    and Peters et al, Pharmacokinetic analysis: A Practical Approach    (1996). Reference is also made to “Pharmacokinetics”, M Gibaldi & D    Perron, published by Marcel Dekker, 2nd Rev. edition (1982). The    terms “increase in half-life” or “increased half-life” as also as    defined in paragraph o) on page 57 of WO 08/020,079 and in    particular refer to an increase in the t1/2-beta, either with or    without an increase in the t1/2-alpha and/or the AUC or both.-   l) In respect of a target or antigen, the term “interaction site” on    the target or antigen means a site, epitope, antigenic determinant,    part, domain or stretch of amino acid residues on the target or    antigen that is a site for binding to a receptor or other binding    partner, a catalytic site, a cleavage site, a site for allosteric    interaction, a site involved in multimerization (such as    homomerization or heterodimerization) of the target or antigen; or    any other site, epitope, antigenic determinant, part, domain or    stretch of amino acid residues on the target or antigen that is    involved in a biological action or mechanism of the target or    antigen. More generally, an “interaction site” can be any site,    epitope, antigenic determinant, part, domain or stretch of amino    acid residues on the target or antigen to which an amino acid    sequence or polypeptide of the invention can bind such that the    target or antigen (and/or any pathway, interaction, biological    mechanism or biological effect in which the target or antigen is    involved) is modulated (as defined herein).-   m) An amino add sequence or polypeptide is said to be “specific for”    a first target or antigen compared to a second target or antigen    when is binds to the first antigen with an affinity (as described    above, and suitably expressed as a K_(D) value, K_(A) value, K_(off)    rate and/or k_(on) rate) that is at least 10 times, such as at least    100 times, and preferably at least 1000 times, and up to 10000 times    or more better than the affinity with which said amino acid sequence    or polypeptide binds to the second target or antigen. For example,    amino acid sequence or polypeptide may bind to the first target or    antigen with a K_(D) value that is at least 10 times less, such as    at least 100 times less, and preferably at least 1000 times less,    such as 10.000 times less or even less than that, than the K_(D)    with which said amino acid sequence or polypeptide binds to the    second target or antigen. Preferably, when an amino acid sequence or    polypeptide is “specific for” a first target or antigen compared to    a second target or antigen, it is directed against (as defined    herein) said first target or antigen, but not directed against said    second target or antigen.-   n) The terms “(cross)-block”, “(cross)-blocked” and    “(cross)-blocking” are used interchangeably herein to mean the    ability of an amino acid sequence or other binding agent (such as a    polypeptide of the invention) to interfere with the binding of other    amino acid sequences or binding agents of the invention to a given    target. The extend to which an amino acid sequence or other binding    agents of the invention is able to interfere with the binding of    another to the target, and therefore whether it can be said to    cross-block according to the invention, can be determined using    competition binding assays. One particularly suitable quantitative    cross-blocking assay uses a Biacore machine which can measure the    extent of interactions using surface plasmon resonance technology.    Another suitable quantitative cross-blocking assay uses an    ELISA-based approach to measure competition between amino acid    sequences or other binding agents in terms of their binding to the    target.    -   The following generally describes a suitable Biacore assay for        determining whether an amino acid sequence or other binding        agent cross-blocks or is capable of cross-blocking according to        the invention. It will be appreciated that the assay can be used        with any of the amino acid sequences or other binding agents        described herein. The Biacore machine (for example the        Biacore 3000) is operated in line with the manufacturer's        recommendations. Thus in one cross-blocking assay, the target        protein is coupled to a CM5 Biacore chip using standard amine        coupling chemistry to generate a surface that is coated with the        target. Typically 200-800 resonance units of the target would be        coupled to the chip (an amount that gives easily measurable        levels of binding but that is readily saturable by the        concentrations of test reagent being used). Two test amino add        sequences (termed A* and B*) to be assessed for their ability to        cross-block each other are mixed at a one to one molar ratio of        binding sites in a suitable buffer to create the test mixture.        When calculating the concentrations on a binding site basis the        molecular weight of an amino acid sequence is assumed to be the        total molecular weight of the amino acid sequence divided by the        number of target binding sites on that amino acid sequence. The        concentration of each amino acid sequence in the test mix should        be high enough to readily saturate the binding sites for that        amino acid sequence on the target molecules captured on the        Biacore chip. The amino acid sequences in the mixture are at the        same molar concentration (on a binding basis) and that        concentration would typically be between 1.00 and 1.5 micromolar        (on a binding site basis). Separate solutions containing A*        alone and B* alone are also prepared. A* and B* in these        solutions should be in the same buffer and at the same        concentration as in the test mix. The test mixture is passed        over the target-coated Biacore chip and the total amount of        binding recorded. The chip is then treated in such a way as to        remove the bound amino acid sequences without damaging the        chip-bound target. Typically this is done by treating the chip        with 30 mM HCl for 60 seconds. The solution of A* alone is then        passed over the target-coated surface and the amount of binding        recorded. The chip is again treated to remove all of the bound        amino acid sequences without damaging the chip-bound target. The        solution of B* alone is then passed over the target-coated        surface and the amount of binding recorded. The maximum        theoretical binding of the mixture of A* and B* is next        calculated, and is the sum of the binding of each amino acid        sequence when passed over the target surface alone. If the        actual recorded binding of the mixture is less than this        theoretical maximum then the two amino acid sequences are        cross-blocking each other. Thus, in general, a cross-blocking        amino acid sequence or other binding agent according to the        invention is one which will bind to the target in the above        Biacore cross-blocking assay such that during the assay and in        the presence of a second amino acid sequence or other binding        agent of the invention the recorded binding is between 80% and        0.1% (e.g. 80% to 4%) of the maximum theoretical binding,        specifically between 75% and 0.1% (e.g. 75% to 4%) of the        maximum theoretical binding, and more specifically between 70%        and 0.1% (e.g. 70% to 4%) of maximum theoretical binding (as        just defined above) of the two amino acid sequences or binding        agents in combination. The Biacore assay described above is a        primary assay used to determine if amino acid sequences or other        binding agents cross-block each other according to the        invention. On rare occasions particular amino acid sequences or        other binding agents may not bind to a target coupled via amine        chemistry to a CM5 Biacore chip (this usually occurs when the        relevant binding site on the target is masked or destroyed by        the coupling to the chip). In such cases cross-blocking can be        determined using a tagged version of the target, for example a        N-terminal His-tagged version. In this particular format, an        anti-His amino acid sequence would be coupled to the Biacore        chip and then the His-tagged target would be passed over the        surface of the chip and captured by the anti-His amino acid        sequence. The cross blocking analysis would be carried out        essentially as described above, except that after each chip        regeneration cycle, new His-tagged target would be loaded back        onto the anti-His amino acid sequence coated surface. In        addition to the example given using N-terminal His-tagged        target, C-terminal His-tagged target could alternatively be        used. Furthermore, various other tags and tag binding protein        combinations that are known in the art could be used for such a        cross-blocking analysis (e.g. HA tag with anti-HA antibodies;        FLAG tag with anti-FLAG antibodies; biotin tag with        streptavidin).    -   The following generally describes an ELISA assay for determining        whether an amino acid sequence or other binding agent directed        against a target cross-blocks or is capable of cross-blocking as        defined herein. It will be appreciated that the assay can be        used with any of the amino acid sequences (or other binding        agents such as polypeptides of the invention) described herein.        The general principal of the assay is to have an amino acid        sequence or binding agent that is directed against the target        coated onto the wells of an ELISA plate. An excess amount of a        second, potentially cross-blocking, anti-target amino acid        sequence is added in solution (i.e. not bound to the ELISA        plate). A limited amount of the target is then added to the        wells. The coated amino acid sequence and the amino acid        sequence in solution compete for binding of the limited number        of target molecules. The plate is washed to remove excess target        that has not been bound by the coated amino acid sequence and to        also remove the second, solution phase amino acid sequence as        well as any complexes formed between the second, solution phase        amino acid sequence and target. The amount of bound target is        then measured using a reagent that is appropriate to detect the        target. An amino acid sequence in solution that is able to        cross-block the coated amino acid sequence will be able to cause        a decrease in the number of target molecules that the coated        amino acid sequence can bind relative to the number of target        molecules that the coated amino acid sequence can bind in the        absence of the second, solution phase, amino acid sequence. In        the instance where the first amino acid sequence, e.g. an Ab-X,        is chosen to be the immobilized amino acid sequence, it is        coated onto the wells of the ELISA plate, after which the plates        are blocked with a suitable blocking solution to minimize        non-specific binding of reagents that are subsequently added. An        excess amount of the second amino acid sequence, i.e. Ab-Y, is        then added to the ELISA plate such that the moles of Ab-Y target        binding sites per well are at least 10 fold higher than the        moles of Ab-X target binding sites that were used, per well,        during the coating of the ELISA plate. Target is then added such        that the moles of target added per well are at least 25-fold        lower than the moles of Ab-X target binding sites that were used        for coating each well. Following a suitable incubation period        the ELISA plate is washed and a reagent for detecting the target        is added to measure the amount of target specifically bound by        the coated anti-target amino acid sequence (in this case Ab-X).        The background signal for the assay is defined as the signal        obtained in wells with the coated amino acid sequence (in this        case Ab-X), second solution phase amino acid sequence (in this        case Ab-Y), target buffer only (i.e. without target) and target        detection reagents. The positive control signal for the assay is        defined as the signal obtained in wells with the coated amino        acid sequence (in this case Ab-X), second solution phase amino        acid sequence buffer only (i.e. without second solution phase        amino acid sequence), target and target detection reagents. The        ELISA assay may be run in such a manner so as to have the        positive control signal be at least 6 times the background        signal. To avoid any artifacts (e.g. significantly different        affinities between Ab-X and Ab-Y for the target) resulting from        the choice of which amino acid sequence to use as the coating        amino acid sequence and which to use as the second (competitor)        amino acid sequence, the cross-blocking assay may to be run in        two formats: 1) format 1 is where Ab-X is the amino acid        sequence that is coated onto the ELISA plate and Ab-Y is the        competitor amino acid sequence that is in solution and 2) format        2 is where Ab-Y is the amino acid sequence that is coated onto        the ELISA plate and Ab-X is the competitor amino acid sequence        that is in solution. Ab-X and Ab-Y are defined as cross-blocking        if, either in format 1 or in format 2, the solution phase        anti-target amino acid sequence is able to cause a reduction of        between 60% and 100%, specifically between 70% and 100%, and        more specifically between 80% and 100%, of the target detection        signal {i.e. the amount of target bound by the coated amino acid        sequence) as compared to the target detection signal obtained in        the absence of the solution phase anti-target amino acid        sequence (i.e. the positive control wells).-   o) An amino acid sequence is said to be “cross-reactive” for two    different antigens or antigenic determinants (such as e.g. serum    albumin from two different species of mammal, such as e.g. human    serum albumin and cyno serum albumin, such as e.g. protein F of    different strains of hRSV, such as e.g. protein F of different    escape mutants of hRSV) if it is specific for (as defined herein)    both these different antigens or antigenic determinants.-   p) As further described herein, the total number of amino acid    residues in a Nanobody® can be in the region of 110-120, is    preferably 112-115, and is most preferably 113. It should however be    noted that parts, fragments, analogs or derivatives (as further    described herein) of a Nanobody® are not particularly limited as to    their length and/or size, as long as such parts, fragments, analogs    or derivatives meet the further requirements outlined herein and are    also preferably suitable for the purposes described herein.-   q) As further described in paragraph q) on pages 58 and 59 of WO    08/020,079 (incorporated herein by reference), the amino acid    residues of a Nanobody® are numbered according to the general    numbering for V_(H) domains given by Kabat et al. (“Sequence of    proteins of immunological interest”, US Public Health Services, NIH    Bethesda, Md., Publication No. 91), as applied to V_(HH) domains    from Camelids in the article of Riechmann and Muyidermans, J.    Immunol. Methods 2000 Jun. 23; 240 (1-2): 185-195 (see for example    FIG. 2 of this publication), and accordingly FR1 of a Nanobody®    comprises the amino acid residues at positions 1-30, CDR1 of a    Nanobody® comprises the amino acid residues at positions 31-35, FR2    of a Nanobody® comprises the amino acids at positions 36-49, CDR2 of    a Nanobody® comprises the amino acid residues at positions 50-65,    FR3 of a Nanobody® comprises the amino acid residues at positions    66-94, CDR3 of a Nanobody® comprises the amino acid residues at    positions 95-102, and FR4 of a Nanobody® comprises the amino acid    residues at positions 103-113.-   r) In the context of the present invention “target host cell (of a    virus)” generally refers to a particular cell, which is or is    derived from a living subject and which is susceptible to infection    by said virus.-   s) The term “infectivity of a virus”, as used herein, refers to the    proportion of living subjects that, when exposed to said virus,    actually become infected by said virus.-   t) The term “neutralization of a virus”, as used herein, refers to    the modulation and/or reduction and/or prevention and/or inhibition    of the infectivity (as defined herein) of a virus by binding of a    neutralizing compound to the virion, as measured using a suitable in    vitro, cellular or in vivo assay (such as e.g. the    microneutralization assay described by Anderson et al. 1985 (J.    Clin. Microbiol. 22: 1050-1052) and 1988 (J. Virol. 62: 4232-4238),    modifications of these assays such as e.g. described in Example 6; a    plaque reduction assay as for example described by Johnson et al.    1997 (J. Inf. Dis. 176: 1215-1224), and modifications thereof and    those mentioned herein). In particular, “neutralizing (a virus)” or    “to neutralize (a virus)” may mean either modulating, reducing,    preventing or inhibiting the infectivity (as defined herein) of a    virus as measured using a suitable in vitro, cellular or in vivo    assay (such as those mentioned herein), by at least 1%, preferably    at least 5%, such as at least 10% or at least 25%, for example by at    least 50%, at least 60%, at least 70%, at least 80%, or 90% or more,    compared to normal (i.e. naturally occurring) infectivity (as    defined herein) of a virus, in the same assay under the same    conditions but without the presence of the amino acid sequence,    Nanobody® or polypeptide of the invention.-   u) The term “potency of an amino acid sequence of the invention”,    “potency of a Nanobody® of the invention”, “potency of a polypeptide    of the invention”, and/or “potency of compound or construct of the    invention”, as used herein, refers to the capacity of said amino    acid sequence of the invention, Nanobody® of the invention,    polypeptide of the invention, and/or compound or construct of the    invention to neutralize a particular virus (such as e.g. hRSV), to    modulate, inhibit and/or prevent infectivity of a virus, to    modulate, inhibit and/or prevent fusion of a virus with (the cell    membrane of) the target host cell, and/or to modulate, inhibit    and/or prevent entry of a virus into the target host cell (as    defined herein). The potency may be measured by any suitable assay    known in the art or described herein, such as e.g. the    micro-neutralization assays as described in the Example section    and/or the assays mentioned in point t) above.-   v) The term “virus attachment”, as used herein, is attachment of a    virus (e.g. hRSV) to a target host cell directly (for example by    interacting with a viral receptor) or indirectly (for example by    mediating the interaction of one or more other proteins or molecules    to a viral receptor),-   w) The term “virus fusion”, as used herein, is fusion of a virus    (e.g. hRSV) to a target host cell directly (for example by    interacting with membrane compounds of the target host cell) or    indirectly (for example by mediating the interaction of one or more    other proteins or molecules with membrane compounds of the target    host cell).-   x) The term “viral entry” used herein encompasses any viral-mediated    biological pathway that is needed to accomplish virion attachment to    a target host cell and/or viral fusion with a target host cell.-   y) A “stretch of amino acid residues” means two or more amino acid    residues that are adjacent to each other or in close proximity to    each other, i.e. in the primary or tertiary structure of the amino    acid sequence. In the context of the present invention, the “stretch    of amino acid residues” will be (at least partially) responsible for    the binding of the amino acid sequence, Nanobody®, polypeptide,    compound or construct of the invention to antigenic site II on    protein F of hRSV.-   z) When comparing two stretches of amino acid residues (or two CDR    sequences), the term “amino acid difference” refers to an insertion,    deletion or substitution of a single amino acid residue on a    position of the stretch of amino acid residues (or CDR sequence)    specified in b), d) or f), compared to the stretch of amino acid    residues (or CDR sequence) of respectively a), c) or e); it being    understood that the stretch of amino acid residues (or CDR sequence)    of b), d) and f) can contain one, two or maximal three such amino    acid differences compared to the stretch of amino acid residues of    respectively a), c) or e).    -   The “amino acid difference” can be any one, two or maximal three        substitutions, deletions and/or insertions, or any combination        thereof, that either improve the properties of the amino acid        sequence of the invention or that at least do not detract too        much from the desired properties or from the balance or        combination of desired properties of the amino acid sequence of        the invention. In this respect, the resulting amino acid        sequence of the invention should at least bind protein F of hRSV        with the same, about the same, or a higher affinity compared to        the amino acid sequence comprising the one or more stretches of        amino acid residues without the one, two or maximal three        substitutions, deletions and/or insertions, said affinity as        measured by surface plasmon resonance; and/or the resulting        amino acid sequence of the invention should at least have a        potency that is the same, about the same or higher compared to        the amino acid sequence comprising the one or more stretches of        amino acid residues without the one, two or maximal three        substitutions, deletions and/or insertions. The skilled person        will generally be able to determine and select suitable        substitutions, deletions and/or insertions, or suitable        combinations thereof, based on the disclosure herein and        optionally after a limited degree of routine experimentation,        which may for example involve introducing a limited number of        possible substitutions, deletions or insertions and determining        their influence on the properties of the amino acid sequences        thus obtained.    -   For example, and depending on the host organism used to express        the amino acid sequence of the invention, such deletions and/or        substitutions may be designed in such a way that one or more        sites for post-translational modification (such as one or more        glycosylation sites) are removed, as will be within the ability        of the person skilled in the art.    -   In a preferred aspect of the invention, the “amino acid        difference” is an amino acid substitution. The amino acid        substitution may be any one, two or maximal three substitutions        that either improve the properties of the amino acid sequence of        the invention or that at least do not detract too much from the        desired properties or from the balance or combination of desired        properties of the amino acid sequence of the invention. In this        respect, the resulting amino acid sequence of the invention        should at least bind protein F of hRSV with the same, about the        same, or a higher affinity compared to the amino acid sequence        comprising the one or more stretches of amino acid residues        without the one, two or maximal three substitutions, said        affinity as measured by surface plasmon resonance; and/or the        resulting amino acid sequence of the invention should at least        have a potency that is the same, about the same or higher        compared to the amino acid sequence comprising the one or more        stretches of amino acid residues without the one, two or maximal        three substitutions, deletions and/or insertions. The skilled        person will generally be able to determine and select suitable        substitutions, based on the disclosure herein and optionally        after a limited degree of routine experimentation, which may for        example involve introducing a limited number of possible        substitutions and determining their influence on the properties        of the Nanobodies® thus obtained.    -   The amino acid substitution in the one or more stretches of        amino acid residues may be a conservative amino acid        substitution. “Conservative” amino acid substitutions are        generally amino acid substitutions in which an amino acid        residue is replaced with another amino acid residue of similar        chemical structure and which has little or essentially no        influence on the function, activity or other biological        properties of the resulting amino acid sequence. Such        conservative amino acid substitutions are well known in the art,        for example from WO 04/037999, GB-A-3 357 768, WO 98/49185, WO        00/46383 and WO 01/09300; and (preferred) types and/or        combinations of such substitutions may be selected on the basis        of the pertinent teachings from WO 04/037999 as well as WO        98/49185 and from the further references cited therein.    -   Such conservative substitutions preferably are substitutions in        which one amino acid within the following groups (a)-(e) is        substituted by another amino acid residue within the same        group: (a) small aliphatic, nonpolar or slightly polar residues:        Ala, Ser, Thr, Pro and Gly; (b) polar, negatively charged        residues and their (uncharged) amides: Asp, Asn, Glu and        Gln; (c) polar, positively charged residues: His, Arg and        Lys; (d) large aliphatic, nonpolar residues: Met, Leu, Ile, Val        and Cys; and (e) aromatic residues: Phe, Tyr and Trp.    -   Particularly preferred conservative substitutions are as        follows: Ala into Gly or into Ser; Arg into Lys; Asn into Gln or        into His; Asp into Glu; Cys into Ser; Gln into Asn; Glu into        Asp; Gly into Ala or into Pro; His into Asn or into Gln; Ile        into Leu or into Val; Leu into Ile or into Val; Lys into Arg,        into Gln or into Glu; Met into Leu, into Tyr or into Ile; Phe        into Met, into Leu or into Tyr; Ser into Thr; Thr into Ser; Trp        into Tyr; Tyr into Trp; and/or Phe into Val, into Ile or into        Leu. The amino acid substitution in the one or more stretches of        amino acid residues may provide the amino acid sequence with        increased affinity for binding to protein F of hRSV. This may be        done by techniques such as random or site-directed mutagenesis        and/or other techniques for affinity maturation known per se,        such as e.g. described in WO 09/004,065, WO 05/003345, WO        06/023144, EP527809, EP397834.    -   Without being limiting, rules (partly or fully followed) for        substitutions of amino acid residues in the CDRs may be as        follows (i.e. substitution with amino acids with similar side        chain chemistries):        -   K is substituted by R;        -   R is substituted by K;        -   A is substituted by S or T;        -   S is substituted by A or T;        -   T is substituted by A or 5;        -   I is substituted by L or V;        -   L is substituted by I or V;        -   V is substituted by I or L;        -   F is substituted by Y;        -   Y is substituted by F;        -   N is substituted by D;        -   D is substituted by N;        -   Q is substituted by E;        -   E is substituted by Q;        -   G is substituted by A;        -   M is substituted by L;        -   H, C, W and P are kept constant.    -   Furthermore, and also without being limiting, the rules (partly        or fully followed) for substitutions of amino acid residues in        the CDRs may be alternatively as follows for substitutions at        positions 27 to 35 and positions 50 to 58 (using Kabat numbering        system), wherein for positions 27 to 35:        -   Original amino acid residue in position 27 (Kabat numbering            used) is substituted by F; G; R; S; 2 out of F, G, R, S; 3            out of F, G, R, S; or all of them, preferably all of them;        -   Original amino acid residue in position 28 (Kabat numbering            used) is substituted by A; I; S; T; 2 out of A, I, S, T; 3            out of A, I, S, T; or all of them, preferably all of them;        -   Original amino acid residue in position 29 (Kabat numbering            used) is substituted by F; G; L; S; 2 out of F, G, L, 5; 3            out of F, G, L, 5; or all of them, preferably all of them;        -   Original amino acid residue in position 30 (Kabat numbering            used) is substituted by D; G; S; T; 2 out of D, G, S, T; 3            out of D, G, S, T; or all of them, preferably all of them;        -   Original amino acid residue in position 31 (Kabat numbering            used) is substituted by D; I; N; S; T; 2 out of D, I, N, S,            T; 3 out of D, I, N, S, T; or all of them, preferably all of            them;        -   Original amino acid residue in position 32 (Kabat numbering            used) is substituted by D; N; Y; 2 out of D, N, Y; or all of            them, preferably all of them;        -   Original amino acid residue in position 33 (Kabat numbering            used) is substituted by A; G; T; V; 2 out of A, G, T, V; 3            out of A, G, T, V; or all of them, preferably all of them;        -   Original amino acid residue in position 34 (Kabat numbering            used) is substituted by I; M; or all of them, preferably all            of them;        -   Original amino acid residue in position 35 (Kabat numbering            used) is substituted by A; G; S; 2 out of A, G, S; or all of            them, preferably all of them;    -   and positions 50 to 58 if original amino acid sequence has an        amino acid sequence in position 52a (Kabat numbering used),        -   Original amino acid residue in position 50 (Kabat numbering            used) is substituted by A; C; G; S; T; 2 out of A, C, G, S,            T; 3 out of A, C, G, S, T; 4 out of A, C, G, S, T; or all of            them, preferably all of them;        -   Original amino acid residue in position 51 (Kabat numbering            used) is substituted by I;        -   Original amino acid residue in position 52 (Kabat numbering            used) is substituted by N; R; S; T; 2 out of N, R, S, T; 3            out of N, R, S, T; or all of them, preferably all of them;        -   Original amino acid residue in position 52a (Kabat numbering            used) is substituted by R; 5; T; W; 2 out of R, S, T, W; 3            out of R, S, T, W; or all of them, preferably all of them;        -   Original amino acid residue in position 53 (Kabat numbering            used) is substituted by D; G; N; S; T; 2 out of D, G, N, S,            T; 3 out of D, G, N, S, T; 4 out of D, G, N, S, T; or all of            them, preferably all of them;        -   Original amino acid residue in position 54 (Kabat numbering            used) is substituted by D; or all of them, preferably all of            them;        -   Original amino acid residue in position 55 (Kabat numbering            used) is substituted by D; G; S; 2 out of D, G, 5; or all of            them, preferably all of them;        -   Original amino acid residue in position 56 (Kabat numbering            used) is substituted by I; N; R; S; T; 2 out of I, N, R, S,            T; 3 out of I, N, R, S, T; 4 out of I, N, R, S, T; or all of            them, preferably all of them;        -   Original amino acid residue in position 57 (Kabat numbering            used) is substituted by T;        -   Original amino acid residue in position 58 (Kabat numbering            used) is substituted by D; H; N; S; Y; 2 out of D, H, N, S,            Y; 3 out of 0, H, N, S, Y; 4 out of 0, H, N, S, Y; or all of            them, preferably all of them;    -   and wherein for positions 50 to 58 if original amino acid        sequence has not an amino acid sequence in position 52a (Kabat        numbering used),        -   Original amino acid residue in position 50 (Kabat numbering            used) is substituted by A; C; R; S; T; 2 out of A, G, R, S,            T; 3 out of A, G, R, S, T; 4 out of A, G, R, S, T; or all of            them, preferably all of them;        -   Original amino acid residue in position 51 (Kabat numbering            used) is substituted by I;        -   Original amino acid residue in position 52 (Kabat numbering            used) is substituted by N; S; T; 2 out of N, S, T; or all of            them, preferably all of them;        -   Original amino acid residue in position 53 (Kabat numbering            used) is substituted by N; R; S; T; Y; 2 out of N, R, S, T,            Y; 3 out of N, R, S, T, Y; 4 out of N, R, S, T, Y; or all of            them, preferably all of them;        -   Original amino acid residue in position 54 (Kabat numbering            used) is substituted by D; G; R; S; 2 out of D, G, R, S; 3            out of D, G, R, S; or all of them, preferably all of them;        -   Original amino acid residue in position 55 (Kabat numbering            used) is substituted by G;        -   Original amino acid residue in position 56 (Kabat numbering            used) is substituted by G; N; R; S; T; 2 out of D, N, R, S,            T; 3 out of D, N, R, S, T; 4 out of D, N, R, S, T; or all of            them, preferably all of them;        -   Original amino acid residue in position 57 (Kabat numbering            used) is substituted by T;        -   Original amino acid residue in position 58 (Kabat numbering            used) is substituted by D; N; T; Y; 2 out of D, N, T, Y; 3            out of D, N, T, Y; or all of them, preferably all of them.    -   after which one or more of the potentially useful substitutions        (or combinations thereof) thus determined can be introduced into        said CDR sequence (in any manner known per se, as further        described herein) and the resulting amino acid sequence(s) can        be tested for affinity for protein F of hRSV, and/or for other        desired properties such as e.g. improved binding characteristics        (suitably measured and/or expressed as a K_(D)-value (actual or        apparent), a K_(A)-value (actual or apparent), a k_(on)-rate        and/or a k_(off)-rate, or alternatively as an IC₅₀ value, as        further described herein), improved affinity and/or improved        avidity for protein F of hRSV and/or improved efficacy and/or        potency for neutralizing hRSV. In this way, by means of a        limited degree of trial and error, other suitable substitutions        in the CDRs (or suitable combinations thereof) can be determined        by the skilled person based on the disclosure herein. The amino        acid sequences comprising a stretch of amino acid residues that        has one, two or maximal three substitutions, insertions or        deletions, and nucleic acid sequences encoding the same, can be        provided in any manner known per se, for example using one or        more of the techniques mentioned on pages 103 and 104 of WO        08/020,079.    -   The resulting amino acid sequences of the invention should        preferably bind to protein F of hRSV with an affinity (suitably        measured and/or expressed as a K_(D)-value (actual or apparent),        a K_(A)-value (actual or apparent), a k_(on)-rate and/or a        k_(off)-rate, or alternatively as an IC₅₀ value, as further        described herein) that is as defined herein; and/or neutralize        hRSV with an efficacy and/or potency that is as defined herein.-   aa) When comparing two amino acid sequences, the term “amino acid    difference” refers to an insertion, deletion or substitution of a    single amino acid residue on a position of the first amino acid    sequence, compared to the second amino acid sequence; it being    understood that two amino acid sequences can contain one, two or    maximal three such amino acid differences. The “amino acid    difference” can be any one, any two or maximal any three    substitutions, deletions or insertions in the amino acid sequence,    i.e. in one or more of the framework regions or in one or more of    the CDRs (which may be in a CDR of the invention (i.e. in CDR2) or    in another CDR (i.e. in CDR1, CDR2 or CDR3)), or any combination    thereof, that either improve the properties of the amino acid    sequence of the invention or that at least do not detract too much    from the desired properties or from the balance or combination of    desired properties of the amino acid sequence of the invention. In    this respect, the resulting amino acid sequence of the invention    should at least bind protein F of hRSV with the same, about the    same, or a higher affinity compared to the amino acid sequence    without the one, two or maximal three substitutions, deletions or    insertions, said affinity as measured by surface plasmon resonance;    and/or the resulting amino acid sequence of the invention should at    least have a potency that is the same, about the same or higher    compared to the amino acid sequence without the one, two or maximal    three substitutions, deletions and/or insertions. The skilled person    will generally be able to determine and select suitable    substitutions, deletions or insertions, or suitable combinations    thereof, based on the disclosure herein and optionally after a    limited degree of routine experimentation, which may for example    involve introducing a limited number of possible substitutions,    deletions or insertions and determining their influence on the    properties of the amino acid sequence thus obtained.    -   In one aspect of the invention, the “amino acid difference” is        an amino acid substitution. The amino acid substitution may be        any one, two or maximal three substitutions in one or more of        the framework regions or in one or more of the CDRs (which may        be in a CDR of the invention (i.e. in CDR2) or in another CDR        (i.e. in CDR1, CDR2 or CDR3)), or any combination thereof, that        either improve the properties of the amino acid sequence of the        invention or that at least do not detract too much from the        desired properties or from the balance or combination of desired        properties of the amino acid sequence of the invention. In this        respect, the resulting amino acid sequence of the invention        should at least bind protein F of hRSV with the same, about the        same, or a higher affinity compared to the amino acid sequence        without the one, two or maximal three substitutions, said        affinity as measured by surface plasmon resonance; and/or the        resulting amino acid sequence of the invention should at least        have a potency that is the same, about the same or higher        compared to the amino acid sequence without the one, two or        maximal three substitutions. The skilled person will generally        be able to determine and select suitable substitutions, based on        the disclosure herein and optionally after a limited degree of        routine experimentation, which may for example involve        introducing a limited number of possible substitutions and        determining their influence on the properties of the amino acid        sequences thus obtained.    -   As indicated above, the substitutions, insertions or deletions        can be in one or more of the framework regions and/or in one or        more of the CDR's. As discussed above (see point z) above), the        amino acid substitution in one or more of the CDRs can be any        substitution such as a “conservative substitution” (as defined        herein), it may be driven by certain rules (as defined herein),        and/or it may induce improved properties to the resulting amino        acid sequences. When such substitutions, insertions or deletions        are made in one or more of the framework regions, they may be        made at one or more of the Hallmark residues (as e.g. defined in        WO 08/020,079; Tables A-3 to A-8) and/or at one or more of the        other positions in the framework residues, although        substitutions, insertions or deletions at the Hallmark residues        are generally less preferred (unless these are suitable        humanizing substitutions as described herein). By means of        non-limiting examples, a substitution may for example be a        conservative substitution (as described herein) and/or an amino        acid residue may be replaced by another amino acid residue that        naturally occurs at the same position in another V_(HH) domain        (see WO 08/020,079, Tables A-5 to A-8), although the invention        is generally not limited thereto.    -   Substitutions, insertions or deletions made (preferably) in one        or more of the framework regions may be humanizing substitution        (i.e. replacing one or more amino acid residues in the amino        acid sequence of a naturally occurring V_(HH) sequence (and in        particular in the framework sequences) by one or more of the        amino acid residues that occur at the corresponding position(s)        in a V_(H) domain from a conventional 4-chain antibody from a        human being). Some preferred, but non-limiting humanizing        substitutions (and suitable combinations thereof) will become        clear to the skilled person based on the disclosure herein.        Potentially useful humanizing substitutions can be ascertained        by comparing the sequence of the framework regions of one of the        amino acid sequence of the invention defined in a) with the        corresponding framework sequence of one or more closely related        human V_(H) sequences, after which one or more of the        potentially useful humanizing substitutions (or combinations        thereof) thus determined can be introduced into said amino acid        sequence of the invention defined in a) (in any manner known per        se, as further described herein) and the resulting humanized        amino acid sequence can be tested for affinity for protein F of        hRSV, for stability, for ease and level of expression, and/or        for other desired properties defined herein. In this way, by        means of a limited degree of trial and error, other suitable        humanizing substitutions (or suitable combinations thereof) can        be determined by the skilled person based on the disclosure        herein.    -   The humanizing substitutions should be chosen such that the        resulting humanized amino acid sequence and/or Nanobody® still        retains the favourable properties of Nanobodies® as defined        herein. A skilled person will generally be able to determine and        select suitable humanizing substitutions or suitable        combinations of humanizing substitutions, based on the        disclosure herein and optionally after a limited degree of        routine experimentation, which may for example involve        introducing a limited number of possible humanizing        substitutions and determining their influence on the properties        of the Nanobodies® thus obtained. Generally, as a result of        humanization, the amino acid sequence and/or Nanobody® of the        invention may become more “human-like”, while still retaining        the favorable properties of the Nanobodies® of the invention as        described herein. As a result, such humanized amino acid        sequence and/or Nanobody® may have several advantages, such as a        reduced immunogenicity, compared to the corresponding naturally        occurring V_(HH) domain. Again, based on the disclosure herein        and optionally after a limited degree of routine        experimentation, the skilled person will be able to select        humanizing substitutions or suitable combinations of humanizing        substitutions which optimize or achieve a desired or suitable        balance between the favourable properties provided by the        humanizing substitutions on the one hand and the favourable        properties of naturally occurring V_(HH) domains on the other        hand.    -   The amino acid sequences and/or Nanobodies® of the invention may        be suitably humanized at any framework residue(s), such as at        one or more Hallmark residues (as defined herein) or at one or        more other framework residues (i.e. non-Hallmark residues) or        any suitable combination thereof. One preferred humanizing        substitution for Nanobodies® of the “P,R,S-103 group” or the        “KERE group” (as defined in WO 08/020,079) is Q108 into L108.    -   Depending on the host organism used to express the amino acid        sequence, Nanobody® or polypeptide of the invention, such        deletions and/or substitutions may also be designed in such a        way that one or more sites for post-translational modification        (such as one or more glycosylation sites) are removed, as will        be within the ability of the person skilled in the art.        Alternatively, substitutions or insertions may be designed so as        to introduce one or more sites for attachment of functional        groups (as described herein), for example to allow site-specific        pegylation (again as described herein).    -   As can be seen from the data on the V_(HH) entropy and V_(HH)        variability given in Tables A-5-A-8 of WO 08/020,079, some amino        acid residues in the framework regions are more conserved than        others. Generally, although the invention in its broadest sense        is not limited thereto, any substitutions, deletions or        insertions are preferably made at positions that are less        conserved. Also, generally, amino acid substitutions are        preferred over amino acid deletions or insertions. Any amino        acid substitutions applied to the polypeptides described herein        may also be based on the analysis of the frequencies of amino        acid variations between homologous proteins of different species        developed by Schulz et al., Principles of Protein Structure,        Springer-Verlag, 1978, on the analyses of structure forming        potentials developed by Chou and Fasman, Biochemistry 13: 211,        1974 and Adv. Enzymol., 47: 45-149, 1978, and on the analysis of        hydrophobicity patterns in proteins developed by Eisenberg et        al., Proc. Natl. Acad. Sci. USA 81: 140-144, 1984; Kyte &        Doolittle; J Molec. Biol. 157: 105-132, 198 1, and Goldman et        al., Ann. Rev. Biophys. Chem. 15: 321-353, 1986, all        incorporated herein in their entirety by reference. Information        on the primary, secondary and tertiary structure of Nanobodies®        is given in the description herein and in the general background        art cited above. Also, for this purpose, the crystal structure        of a V_(HH) domain from a llama is for example given by Desmyter        et al., Nature Structural Biology, Vol. 3, 9, 803 (1996);        Spinelli et al., Natural Structural Biology (1996); 3, 752-757;        and Decanniere et al., Structure, Vol. 7, 4, 361 (1999). Further        information about some of the amino acid residues that in        conventional V_(H) domains form the V_(H)/V_(L) interface and        potential camelizing substitutions on these positions can be        found in the prior art cited above.    -   The amino acid sequences and/or Nanobodies® with one, two or        maximal three substitutions, insertions or deletions, and        nucleic acid sequences encoding the same, can be provided in any        manner known per se, for example using one or more of the        techniques mentioned on pages 103 and 104 of WO 08/020,079.    -   The resulting amino acid sequences and/or Nanobodies® of the        invention should preferably bind to protein F of hRSV with an        affinity (suitably measured and/or expressed as a K_(D)-value        (actual or apparent), a K_(A)-value (actual or apparent), a        k_(on)-rate and/or a k_(off)-rate, or alternatively as an IC₅₀        value, as further described herein) that is as defined herein;        and/or neutralize hRSV with an efficacy and/or potency that is        as defined herein.-   bb) When comparing two polypeptides, the term “amino acid    difference” refers to an insertion, deletion or substitution of a    single amino acid residue on a position of the first polypeptide,    compared to the second polypeptide; it being understood that two    polypeptides can contain one, two or maximal three such amino acid    differences.    -   The “amino acid difference” can be any one, any two or maximal        three substitutions, deletions or insertions in the polypeptide,        i.e. in one or more of the framework regions or in one or more        of the CDRs (which may be in a CDR of the invention (i.e. in        CDR2) or in another CDR (i.e. in CDR1, CDR2 or CDR3)), or any        combination thereof, that either improve the properties of the        polypeptide of the invention or that at least do not detract too        much from the desired properties or from the balance or        combination of desired properties of the polypeptide of the        invention. In this respect, the resulting polypeptide of the        invention should at least bind protein F of hRSV with the same,        about the same, or a higher affinity compared to the polypeptide        without the one, two or maximal three substitutions, deletions        or insertions, said affinity as measured by surface plasmon        resonance; and/or the resulting polypeptide of the invention        should at least have a potency that is the same, about the same        or higher compared to the polypeptide without the one, two or        maximal three substitutions, deletions and/or insertions. The        resulting polypeptide should preferably bind to protein F of        hRSV with an affinity (suitably measured and/or expressed as a        K_(D)-value (actual or apparent), a K_(A)-value (actual or        apparent), a k_(on)-rate and/or a k_(off)-rate, or alternatively        as an IC₅₀ value, as further described herein) that is as        defined herein; and/or neutralize hRSV with an efficacy and/or        potency that is as defined herein. The skilled person will        generally be able to determine and select suitable        substitutions, deletions or insertions, or suitable combinations        thereof, based on the disclosure herein and optionally after a        limited degree of routine experimentation, which may for example        involve introducing a limited number of possible substitutions,        deletions or insertions and determining their influence on the        properties of the polypeptide thus obtained.    -   In one aspect of the invention, the “amino acid difference” is        an amino acid substitution. The amino acid substitution may be        any one, any two or maximal any three substitutions in the        framework regions or in one or more of the CDRs (which may be in        a CDR of the invention (i.e. present in CDR2) or in another CDR        (i.e. in CDR1, CDR2 or CDR3)), or any combination thereof, that        either improve the properties of the polypeptide of the        invention or that at least do not detract too much from the        desired properties or from the balance or combination of desired        properties of the polypeptide of the invention. In this respect,        the resulting polypeptide of the invention should at least bind        protein F of hRSV with the same, about the same, or a higher        affinity compared to the polypeptide without the one, two or        maximal three substitutions, deletions or insertions, said        affinity as measured by surface plasmon resonance; and/or the        resulting polypeptide of the invention should at least have a        potency that is the same, about the same or higher compared to        the polypeptide without the one, two or maximal three        substitutions, deletions and/or insertions. The resulting        polypeptide should preferably bind to protein F of hRSV with an        affinity (suitably measured and/or expressed as a K_(D)-value        (actual or apparent), a K_(A)-value (actual or apparent), a        k_(on)-rate and/or a k_(off)-rate, or alternatively as an IC₅₀        value, as further described herein) that is as defined herein;        and/or neutralize hRSV with an efficacy and/or potency that is        as defined herein. The skilled person will generally be able to        determine and select suitable substitutions, based on the        disclosure herein and optionally after a limited degree of        routine experimentation, which may for example involve        introducing a limited number of possible substitutions and        determining their influence on the properties of polypeptides        thus obtained.    -   As indicated above, the substitutions, insertions or deletions        can be in one or more of the framework regions and/or in one or        more of the CDR's. As discussed above (see point z)), the        substitutions, insertions or deletions in the CDR's may be any        possible substitutions, insertions or deletions such as        “conservative substitution” (as defined herein), it may be        driven by certain rules (as defined herein), and/or it may        induce improved properties to the resulting polypeptides.    -   When such substitutions, insertions or deletions are made in one        or more of the framework regions, they may be made at one or        more of the Hallmark residues (as e.g. defined in WO 08/020,079;        Tables A-3 to A-8) and/or at one or more of the other positions        in the framework residues, although substitutions, insertions or        deletions at the Hallmark residues are generally less preferred        (unless these are suitable humanizing substitutions as described        herein). By means of non-limiting examples, a substitution may        for example be a conservative substitution (as described herein)        and/or an amino acid residue may be replaced by another amino        acid residue that naturally occurs at the same position in        another V_(HH) domain (see WO 08/020,079, Tables A-5 to A-8),        although the invention is generally not limited thereto.    -   Substitutions, insertions or deletions made (preferably) in one        or more of the framework regions may be humanizing substitution.        Some preferred, but non-limiting humanizing substitutions (and        suitable combinations thereof) will become clear to the skilled        person based on the disclosure herein. Potentially useful        humanizing substitutions can be ascertained by comparing the        sequence of the framework regions of one of the amino acid        sequences encompassed in the polypeptide of the invention        defined in a) with the corresponding framework sequence of one        or more closely related human V_(H) sequences, after which one        or more of the potentially useful humanizing substitutions (or        combinations thereof) thus determined can be introduced into        said polypeptide of the invention defined in a) (in any manner        known per se, as further described herein) and the resulting        polypeptide sequence can be tested for affinity for protein F of        hRSV, for stability, for ease and level of expression, and/or        for other desired properties defined herein. In this way, by        means of a limited degree of trial and error, other suitable        humanizing substitutions (or suitable combinations thereof) can        be determined by the skilled person based on the disclosure        herein.    -   The humanizing substitutions should be chosen such that the        resulting humanized polypeptide sequences still retain the        favourable properties of Nanobodies® encompassed in the        polypeptide as defined herein. A skilled person will generally        be able to determine and select suitable humanizing        substitutions or suitable combinations of humanizing        substitutions, based on the disclosure herein and optionally        after a limited degree of routine experimentation, which may for        example involve introducing a limited number of possible        humanizing substitutions and determining their influence on the        properties of the Nanobodies® encompassed in the polypeptide        thus obtained.    -   Generally, as a result of humanization, the polypeptide of the        invention may become more “human-like”, while still retaining        the favorable properties of the Nanobodies® of the invention        encompassed in the polypeptide as described herein. As a result,        such humanized polypeptides may have several advantages, such as        a reduced immunogenicity, compared to the polypeptides that        encompass corresponding naturally occurring V_(HH) domains.        Again, based on the disclosure herein and optionally after a        limited degree of routine experimentation, the skilled person        will be able to select humanizing substitutions or suitable        combinations of humanizing substitutions which optimize or        achieve a desired or suitable balance between the favourable        properties provided by the humanizing substitutions on the one        hand and the favourable properties of naturally occurring V_(HH)        domains on the other hand.

Polypeptides of the invention may be suitably humanized at any frameworkresidue(s), such as at one or more Hallmark residues (as defined herein)or at one or more other framework residues (i.e. non-Hallmark residues)or any suitable combination thereof. One preferred humanizingsubstitution for Nanobodies® of the “P,R,S-103 group” or the “KEREgroup” is Q108 into L108.

-   -   Depending on the host organism used to express the polypeptide        of the invention, such deletions and/or substitutions may also        be designed in such a way that one or more sites for        post-translational modification (such as one or more        glycosylation sites) are removed, as will be within the ability        of the person skilled in the art. Alternatively, substitutions        or insertions may be designed so as to introduce one or more        sites for attachment of functional groups (as described herein),        for example to allow site-specific pegylation (again as        described herein). As can be seen from the data on the V_(HH)        entropy and V_(HH) variability given in Tables A-5-A-8 of WO        08/020,079, some amino acid residues in the framework regions        are more conserved than others. Generally, although the        invention in its broadest sense is not limited thereto, any        substitutions, deletions or insertions are preferably made at        positions that are less conserved. Also, generally, amino acid        substitutions are preferred over amino acid deletions or        insertions. Any amino acid substitutions applied to the        polypeptides described herein may also be based on the analysis        of the frequencies of amino acid variations between homologous        proteins of different species developed by Schulz et al.,        Principles of Protein Structure, Springer-Verlag, 1978, on the        analyses of structure forming potentials developed by Chou and        Fasman, Biochemistry 13: 211, 1974 and Adv. Enzymol., 47:        45-149, 1978, and on the analysis of hydrophobicity patterns in        proteins developed by Eisenberg et al., Proc. Natl. Acad. Sci.        USA 81: 140-144, 1984; Kyte & Doolittle; J Molec. Biol. 157:        105-132, 198 1, and Goldman et al., Ann. Rev. Biophys. Chem. 15:        321-353, 1986, all incorporated herein in their entirety by        reference. Information on the primary, secondary and tertiary        structure of Nanobodies® is given in the description herein and        in the general background art cited above. Also, for this        purpose, the crystal structure of a V_(HH) domain from a llama        is for example given by Desmyter et al., Nature Structural        Biology, Vol. 3, 9, 803 (1996); Spinelli et al., Natural        Structural Biology (1996); 3, 752-757; and Decanniere et al.,        Structure, Vol. 7, 4, 361 (1999). Further information about some        of the amino acid residues that in conventional V_(H) domains        form the V_(H)/V_(L) interface and potential camelizing        substitutions on these positions can be found in the prior art        cited above.    -   The polypeptides with one, two or maximal three substitutions,        insertions or deletions, and nucleic acid sequences encoding the        same, can be provided in any manner known per se, for example        using one or more of the techniques mentioned on pages 103 and        104 of WO 08/020,079.    -   The resulting polypeptides of the invention should preferably        bind to protein F of hRSV with an affinity (suitably measured        and/or expressed as a K_(D)-value (actual or apparent), a        K_(A)-value (actual or apparent), a k_(on)-rate and/or a        k_(off)-rate, or alternatively as an IC₅₀ value, as further        described herein) that is as defined herein; and/or neutralize        hRSV with an efficacy and/or potency that is as defined herein.

-   cc) The figures, sequence listing and the experimental part/examples    are only given to further illustrate the invention and should not be    interpreted or construed as limiting the scope of the invention    and/or of the appended claims in any way, unless explicitly    indicated otherwise herein.

For binding to its epitope on protein F of hRSV, an amino acid sequencewill usually contain within its amino acid sequence one or more aminoacid residues or one or more stretches of amino acid residues (asdefined herein; i.e. with each “stretch” comprising two or more aminoacid residues that are adjacent to each other or in close proximity toeach other, i.e. in the primary or tertiary structure of the amino acidsequence) via which the amino acid sequence of the invention can bind toits epitope on protein F of hRSV. These amino acid residues or stretchesof amino acid residues thus form the “site” for binding to the epitopeon protein F of hRSV (also referred to herein as the “antigen bindingsite”; as further defined herein).

The present invention provides a number of stretches of amino acidresidues (as defined herein) that are particularly suited for binding toantigenic site II on protein F of hRSV (for a description of antigenicsites in the hRSV F protein reference is made to Lopez et al. 1998, J.virol. 72: 6922-6928). These stretches of amino acid residues may bepresent in, and/or may be incorporated into, an amino acid sequence ofthe invention, in particular in such a way that they form (part of) theantigen binding site of the amino acid sequence of the invention. Theresulting amino acid sequences will bind a specific epitope on protein Fof hRSV that lies in, forms part of, or overlaps with (i.e. in theprimary or tertiary structure) or is in close proximity to (i.e. in theprimary or tertiary structure) antigenic site II on protein F of hRSV.Also, the resulting amino acid sequences of the invention willpreferably be such that they can compete with Synagis® for binding toprotein F of hRSV; and/or such that they can bind to the same epitope orbinding site on protein F of hRSV as Synagis®, or to an epitope close tosaid binding site and/or overlapping with said binding site.

The present invention provides a stretch of amino acid residues (SEQ IDNO: 102) that is particularly suited for binding to protein F of hRSV.This stretch of amino acid residues (or variants of SEQ ID NO: 102 asdefined herein) may be present in, and/or may be incorporated into, anamino acid sequence of the invention, in particular in such a way thatthey form (part of) the antigen binding site of the amino acid sequenceof the invention. The stretch of amino acid residues has been generatedas CDR2 sequence of a heavy chain antibody or V_(HH) sequence (NC41; SEQID NO: 5) that was raised against protein F of hRSV and that was furthermodified in a library approach to generate humanized NC41 Nanobodies®(as described in the Example section). More in particular, the glycine(Gly, G) residue at position 6 of the CDR2 of NC41 was substituted intoan Aspartic acid (Asp, D) residue. Surprisingly, improved bindingcharacteristics (suitably measured and/or expressed as a K_(D)-value(actual or apparent), a K_(A)-value (actual or apparent), a k_(on)-rateand/or a k_(off)-rate, or alternatively as an IC₅₀ value, as furtherdescribed herein), improved affinity and/or improved avidity for proteinF of hRSV and/or improved efficacy and/or potency for neutralizing hRSVhave been observed for amino acid sequences that comprise this stretchof amino acid residues (SEQ ID NO: 102). This stretch of amino acidresidues (or variants of SEQ ID NO: 102, as defined herein) are alsoreferred to herein as “CDR2 sequences of the invention”.

Accordingly, in one aspect, the present invention provides amino acidsequences that comprise at least a stretch of amino acid residues chosenfrom the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

In a preferred aspect, the present invention provides amino acidsequences that comprise two or more stretches of amino acid residues inwhich one stretch is chosen from the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein of hRSV with the same, about the            same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a) and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).

Even more preferably, the amino acid sequences of the invention comprisethree or more stretches of amino acid residues, in which the firststretch of amino acid residues is chosen from the group consisting of:

-   -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;        the second stretch of amino acid residues is chosen from the        group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;            and the third stretch of amino acid residues is chosen from            the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Amino acid sequences comprising one or more of the above specifiedstretches of amino acid residues show improved properties such as e.g.improved binding characteristics (suitably measured and/or expressed asa K_(D)-value (actual or apparent), a K_(A)-value (actual or apparent),a k_(on)-rate and/or a k_(off)-rate, or alternatively as an IC₅₀ value,as further described herein), improved affinity and/or improved avidityfor protein F of hRSV and/or improved efficacy and/or potency forneutralizing hRSV.

More in particular, the amino acid sequences of the invention comprisingone or more of the above specified stretches of amino acid residues canbind to protein F of hRSV with an affinity (suitably measured and/orexpressed as a K_(D)-value (actual or apparent), a K_(A)-value (actualor apparent), a k_(on)-rate and/or a k_(off)-rate, or alternatively asan IC₅₀ value, as further described herein) preferably such that they:

-   -   bind to protein F of hRSV with a dissociation constant (K_(D))        of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or less,        more preferably 15 nM to 1 nM or even 10 nM to 1 nM or less;        and/or such that they:    -   bind to protein F of hRSV with a k_(on)-rate of between 10⁴ M⁻¹        s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹ s⁻¹ and 10⁷        M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more;        and/or such that they:    -   bind to protein F of hRSV with a k_(off) rate between 10⁻² s⁻¹        (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near irreversible        complex with a t_(1/2) of multiple days), preferably between        10⁻³ s⁻¹ and 10⁻⁴ s⁻², or lower;

Some preferred IC50 values for binding of the amino acid sequences ofthe invention to protein F of hRSV will become clear from the furtherdescription and examples herein.

Assays to determine the IC50 include competition assays such ascompetition ELISA (e.g. competition with Synagis® or its Fab fragment)or more preferably neutralization assays such as the microneutralizationassay described by Anderson et al. (1985, J. Clin. Microbiol. 22:1050-1052; 1988, J. Virol. 62: 4232-4238), modifications of this assaysuch as e.g. described in Example 6, or a plaque reduction assay as forexample described by Johnson et al. (1997, J. Inf. Dis. 176: 1215-4224),and modifications thereof.

For example, in a competition assay with the Fab fragment of Synagis®,the amino acid sequences of the invention may have IC50 values between 1nM and 100 nM, preferably between 10 nM and 50 nM, or less.

For example, in a microneutralization assay on hRSV Long (such as e.g.described in Example 6) the amino acid sequences of the invention mayhave IC50 values between 100 nM and 1000 nM, preferably between 100 nMand 500 nM, or less.

It should be noted that the invention is not limited as to the origin ofthe amino acid sequence of the invention (or of the nucleotide sequenceof the invention used to express it), nor as to the way that the aminoacid sequence or nucleotide sequence of the invention is (or has been)generated or obtained. Thus, the amino acid sequences of the inventionmay be naturally occurring amino acid sequences (from any suitablespecies) or synthetic or semi-synthetic amino acid sequences.

It should be noted that the invention in its broadest sense is notlimited to a specific structural role or function that these stretchesof amino acid residues may have in the amino acid sequence of theinvention, as long as these stretches of amino acid residues allow theamino acid sequence of the invention to bind to antigenic site II onprotein F of hRSV with a certain affinity and/or potency (as definedherein). Thus, generally, the invention in its broadest sense comprisesany amino acid sequence that is capable of binding to antigenic site IIon protein F of hRSV and that comprises one or more stretches of aminoacid residues as defined herein (and in particular a suitablecombination of two or more such stretches of amino acid residues) thatare suitably linked to each other via one or more further amino acidsequences, such that the entire amino acid sequence forms a bindingdomain and/or binding unit that is capable of binding to antigenic siteII on protein F of hRSV.

Such an amino acid sequence may, for example, be a suitable “proteinscaffold” that comprises at least one stretch of amino acid residues asdefined herein (i.e. as part of its antigen binding site). Suitablescaffolds for presenting amino acid sequences will be clear to theskilled person, and for example comprise, without limitation, to bindingscaffolds based on or derived from immunoglobulins, protein scaffoldsderived from protein A domains (such as Affibodies™), tendamistat,fibronectin, lipocalin, CTLA-4, T-cell receptors, designed ankyrinrepeats, avimers and PDZ domains (Binz et al. 2005, Nat. Biotech. 23:1257), and binding moieties based on DNA or RNA including but notlimited to DNA or RNA aptamers (Ulrich et al. 2006, Comb. Chem. HighThroughput Screen 9(8): 619-32).

Again, any amino acid sequence of the invention that comprises one ormore of the stretches of amino acid sequences as defined herein for theamino acid sequences of the invention is preferably such that it canspecifically bind (as defined herein) to protein F of hRSV, and more inparticular such that it can bind to protein F of hRSV with an affinity(suitably measured and/or expressed as a K_(D)-value (actual orapparent), a K_(A)-value (actual or apparent), a k_(on)-rate and/or ak_(off)-rate, or alternatively as an IC₅₀ value, as further describedherein), that is as defined herein. Any amino acid sequence of theinvention that comprises one or more of the stretches of amino acidresidues as defined herein for the amino acid sequences of the inventionis preferably such that it can neutralize hRSV with a potency (asmeasured in a suitable assay as defined herein) that is as definedherein.

Furthermore, it will also be clear to the skilled person that it may bepossible to “graft” one or more of the CDR's defined herein for theamino acid sequences of the invention onto other “scaffolds”, includingbut not limited to human scaffolds or non-immunoglobulin scaffolds.Suitable scaffolds and techniques for such CDR grafting will be clear tothe skilled person and are well known in the art, see for example U.S.Pat. No. 7,180,370, WO 01/27160, EP 0 605 522, EP 0 460 167, U.S. Pat.No. 7,054,297, Nicaise et al., Protein Science (2004), 13:1882-1891;Ewert et al., Methods, 2004 October; 34(2):184-199; Kettleborough etal., Protein Eng. 1991 October; 4(7): 773-783; O'Brien and Jones,Methods Mol. Biol. 2003: 207: 81-100; and Skerra, J. Mat. Recognit.2000: 13: 167-187, and Saerens et al., J. Mol. Biol. 2005 Sep. 23;352(3):597-607, and the further references cited therein. For example,techniques known per se for grafting mouse or rat CDR's onto humanframeworks and scaffolds can be used in an analogous manner to providechimeric proteins comprising one or more of the CDR sequences definedherein for the amino acid sequences of the invention and one or morehuman framework regions or sequences.

In one specific, but non-limiting aspect, the amino acid sequence of theinvention may be an amino acid sequence that comprises an immunoglobulinfold or an amino acid sequence that, under suitable conditions (such asphysiological conditions) is capable of forming an immunoglobulin fold(i.e. by folding). Reference is inter alia made to the review by Halabyet al. (1999, J. Protein Eng. 12: 563-71). Preferably, when properlyfolded so as to form an immunoglobulin fold, the stretches of amino acidresidues may be capable of properly forming the antigen binding site forbinding the specific antigenic site II on protein F of hRSV; and morepreferably capable of binding to antigenic site lion protein F of hRSVwith an affinity (suitably measured and/or expressed as a K_(D)-value(actual or apparent), a K_(A)-value (actual or apparent), a k_(on)-rateand/or a k_(off)-rate, or alternatively as an IC₅₀ value, as furtherdescribed herein) that is as defined herein.

In another specific, but non-limiting aspect, the amino acid sequencesof the invention are immunoglobulin sequences. In particular, butwithout limitation, the amino acid sequences of the invention may beamino acid sequences that essentially consist of 4 framework regions(FR1 to FR4 respectively) and 3 complementarity determining regions(CDR1 to CDR3 respectively); or any suitable fragment of such an aminoacid sequence that still binds antigenic site II on protein F of hRSV.

In such an amino acid sequence of the invention, the framework sequencesmay be any suitable framework sequences, and examples of suitableframework sequences will be clear to the skilled person, for example onthe basis the standard handbooks and the further disclosure and priorart mentioned herein.

The framework sequences are preferably (a suitable combination of)immunoglobulin framework sequences or framework sequences that have beenderived from immunoglobulin framework sequences (for example, byhumanization or camelization). For example, the framework sequences maybe framework sequences derived from a light chain variable domain (e.g.a V_(L)-sequence) and/or from a heavy chain variable domain (e.g. aV_(H)-sequence). When the amino acid sequence of the invention is aheavy chain variable domain sequence, it may be a heavy chain variabledomain sequence that is derived from a conventional four-chain antibody(such as, without limitation, a V_(H) sequence that is derived from ahuman antibody) or be a so-called V_(HH)-sequence (as defined herein)that is derived from a so-called “heavy chain antibody” (as definedherein). In one particularly preferred aspect, the framework sequencesare either framework sequences that have been derived from aV_(HH)-sequence (in which said framework sequences may optionally havebeen partially or fully humanized) or are conventional V_(H) sequencesthat have been camelized (as defined herein).

For a general description of heavy chain antibodies and the variabledomains thereof, reference is inter alia made to the prior art citedherein, as well as to the prior art mentioned on page 59 of WO08/020,079 and to the list of references mentioned on pages 41-43 of theinternational application WO 06/040153, which prior art and referencesare incorporated herein by reference.

The framework sequences may preferably be such that the amino acidsequence of the invention is a domain antibody (or an amino acidsequence that is suitable for use as a domain antibody); is a singledomain antibody (or an amino acid sequence that is suitable for use as asingle domain antibody); is a “dAb” (or an amino acid sequence that issuitable for use as a dAb); or is a Nanobody® (including but not limitedto V_(HH) sequence). Again, suitable framework sequences will be clearto the skilled person, for example on the basis the standard handbooksand the further disclosure and prior art mentioned herein.

In particular, the framework sequences present in the amino acidsequences of the invention may contain one or more of Hallmark residues(as defined in WO 08/020,079 (Tables A-3 to A-8)), such that the aminoacid sequence of the invention is a Nanobody®. Some preferred, butnon-limiting examples of (suitable combinations of) such frameworksequences will become clear from the further disclosure herein (see e.g.Table A-6). Generally, Nanobodies® (in particular V_(HH) sequences andpartially humanized Nanobodies®) can in particular be characterized bythe presence of one or more “Hallmark residues” in one or more of theframework sequences (as e.g. further described in WO 08/020,079, page61, line 24 to page 98, line 3).

As already described herein, the amino acid sequence and structure of aNanobody® can be considered—without however being limited thereto—to becomprised of four framework regions or “FR's”, which are referred to inthe art and herein as “Framework region 1” or “FR1”; as “Frameworkregion 2” or “FR2”; as “Framework region 3” or “FR3”; and as “Frameworkregion 4” or “FR4”, respectively; which framework regions areinterrupted by three complementary determining regions or “CDR's”, whichare referred to in the art as “Complementarity Determining Region 1” or“CDR1”; as “Complementarity Determining Region 2” or “CDR2”; and as“Complementarity Determining Region 3” or “CDR3”, respectively. Somepreferred framework sequences and CDR's (and combinations thereof) thatare present in the Nanobodies® of the invention are as described herein.

Thus, generally, a Nanobody® can be defined as an amino acid sequencewith the (general) structure

-   -   FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4        in which FR1 to FR4 refer to framework regions 1 to 4,        respectively, and in which CDR2 to CDR3 refer to the        complementarity determining regions 1 to 3, respectively, and in        which one or more of the Hallmark residues are as further        defined herein.

In this respect, the amino acid sequences of the invention mayessentially consist of 4 framework regions (FR1 to FR4, respectively)and 3 complementarity determining regions (CDR1 to CDR3, respectively),in which CDR2 is chosen from:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

These preferred complementarity determining regions (CDR2 sequences) arealso referred to as “CDR2(s) of the invention”.

Preferably, the amino acid sequences of the invention may essentiallyconsist of 4 framework regions (FR1 to FR4, respectively) and 3complementarity determining regions (CDR1 to CDR3, respectively), inwhich CDR2 is chosen from the group consisting of:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino add sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;            and at least one of CDR1 or CDR3 is chosen from:    -   CDR1 chosen from the group consisting of:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and/or        -   CDR3 chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Even more preferably, the amino acid sequences of the invention mayessentially consist of 4 framework regions (FR1 to FR4, respectively)and 3 complementarity determining regions (CDR1 to CDR3, respectively),in which:

-   -   CDR1 is chosen from the group consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the ammo acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference; or    -   and        -   CDR2 is chosen from the group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino add residues has an Aspartic add            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and        -   CDR3 is chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein P of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

In a specific aspect, the amino acid sequence or Nanobody® of theinvention comprises at least SEQ ID NO: 102.

In another specific aspect, the amino acid sequence or Nanobody® of theinvention comprises at least SEQ ID NO: 102 and at least one stretch ofamino acid residues (CDR sequence) chosen from:

-   -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Preferably, the amino acid sequence or Nanobody® of the inventioncomprises at least SEQ ID NO: 102 and at least two stretches of aminoacid residues (CDR sequences) in which one stretch is chosen from thegroup consisting of the stretches of amino acid residues defined in a)and b) and in which the other stretch is chosen from the groupconsisting of the stretches of amino acid residues defined in c) and d).

In another specific aspect, the amino acid sequence or Nanobody® of theinvention comprises at least SEQ ID NO: 102 and at least one stretch ofamino acid residues (CDR sequence) chosen from SEQ ID NO: 98 and SEQ IDNO: 121.

Preferably, the amino acid sequence or Nanobody® of the inventioncomprises SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

Preferred combinations of CDR1, CDR2, and CDR3 sequences are also shownin Table A-6.

The amino acid sequences of the invention may essentially consists of aheavy chain variable domain sequence that is derived from a conventionalfour-chain antibody or may essentially consist of a heavy chain variabledomain sequence that is derived from heavy chain antibody. The aminoacid sequences of the invention may essentially consists of a domainantibody (or an amino acid sequence that is suitable for use as a domainantibody), of a single domain antibody (or an amino acid sequence thatis suitable for use as a single domain antibody), of a “dAb” (or anamino acid sequence that is suitable for use as a dAb) or of aNanobody®.

For a general description of (single) domain antibodies, reference isalso made to the prior art cited above, as well as to EP 0 368 684. Forthe term “dAb's”, reference is for example made to Ward et al. (1989,Nature 341: 544-6), to Holt et al., 2003, Trends Biotechnol. 21:484-490; as well as to for example WO 06/030220, WO 06/003388 and otherpublished patent applications of Domantis Ltd. It should also be notedthat, although less preferred in the context of the present inventionbecause they are not of mammalian origin, single domain antibodies orsingle variable domains can be derived from certain species of shark(for example, the so-called “IgNAR domains”, see for example WO05/18629).

In particular, the amino acid sequence of the invention may essentiallyconsist of or may be a Nanobody® (as defined herein) or a suitablefragment thereof. [Note: Nanobody®, Nanobodies® and Nanoclone® areregistered trademarks of Ablynx N. V.]

A Nanobody® can be defined as an amino acid sequence with the (general)structure

FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4

in which FR1 to FR4 refer to framework regions 1 to 4, respectively, andin which CDR1 to CDR3 refer to the complementarity determining regions 1to 3, respectively, and in which one or more of the Hallmark residuesare as defined in WO 08/020,079 (Tables A-3 to A-8).

More in particular, a Nanobody® can be an amino acid sequence with the(general) structure

FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4

in which FR1 to FR4 refer to framework regions 1 to 4, respectively, andin which CDR1 to CDR3 refer to the complementarity determining regions 1to 3, respectively, and which:

-   -   i) have at least 80% amino acid identity with at least one of        the amino acid sequences of SEQ ID NO's: 60-76, 138-141 and        146-157 (see Table A-4), in which for the purposes of        determining the degree of amino acid identity, the amino acid        residues that form the CDR sequences are disregarded. In this        respect, reference is also made to Table A-6, which lists the        framework 1 sequences (SEQ ID NO's: 81-97 and 166), framework 2        sequences (SEQ ID NO's: 99-100), framework 3 sequences (SEQ ID        NO's: 103-120 and 167-168) and framework 4 sequences (SEQ ID        NO's: 123 and 169) of the Nanobodies® of SEQ ID NO's: 60-76,        138-141 and 146-157 (see Table A-4);    -   and in which:    -   ii) preferably one or more of the amino acid residues at        positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according        to the Kabat numbering are chosen from the Hallmark residues        mentioned in Table A-3 to Table A-8 of WO 08/020,079.

For a further general description of Nanobodies®, reference is made tothe prior art cited herein, such as e.g. described in WO 08/020,079(page 16).

Such Nanobodies® may be derived in any suitable manner and from anysuitable source, and may for example be naturally occurring V_(HH)sequences (i.e. from a suitable species of Camelid) or synthetic orsemi-synthetic amino acid sequences.

Again, such Nanobodies® may be derived in any suitable manner and fromany suitable source, and may for example be naturally occurring V_(HH)sequences (i.e. from a suitable species of Camelid) or synthetic orsemi-synthetic amino acid sequences, including but not limited to“humanized” (as defined herein) Nanobodies®, “camelized” (as definedherein) immunoglobulin sequences (and in particular camelized heavychain variable domain sequences), as well as Nanobodies® that have beenobtained by techniques such as affinity maturation (for example,starting from synthetic, random or naturally occurring immunoglobulinsequences), CDR grafting, veneering, combining fragments derived fromdifferent immunoglobulin sequences, PCR assembly using overlappingprimers, and similar techniques for engineering immunoglobulin sequenceswell known to the skilled person; or any suitable combination of any ofthe foregoing as further described herein. Also, when a Nanobody®comprises a V_(HH) sequence, said Nanobody® may be suitably humanized,as further described herein, so as to provide one or more further(partially or fully) humanized Nanobodies® of the invention. Similarly,when a Nanobody® comprises a synthetic or semi-synthetic sequence (suchas a partially humanized sequence), said Nanobody® may optionally befurther suitably humanized, again as described herein, again so as toprovide one or more further (partially or fully) humanized Nanobodies®of the invention.

In particular, humanized Nanobodies® may be amino acid sequences thatare as generally defined for Nanobodies® in the previous paragraphs, butin which at least one amino acid residue is present (and in particular,in at least one of the framework residues) that is and/or thatcorresponds to a humanizing substitution (as defined herein). Somepreferred, but non-limiting humanizing substitutions (and suitablecombinations thereof) will become clear to the skilled person based onthe disclosure herein. In addition, or alternatively, other potentiallyuseful humanizing substitutions can be ascertained by comparing thesequence of the framework regions of a naturally occurring V_(HH)sequence with the corresponding framework sequence of one or moreclosely related human V_(H) sequences, after which one or more of thepotentially useful humanizing substitutions (or combinations thereof)thus determined can be introduced into said V_(HH) sequence (in anymanner known per se, as further described herein) and the resultinghumanized V_(HH) sequences can be tested for affinity for the target,for stability, for ease and level of expression, and/or for otherdesired properties. In this way, by means of a limited degree of trialand error, other suitable humanizing substitutions (or suitablecombinations thereof) can be determined by the skilled person based onthe disclosure herein. Also, based on the foregoing, (the frameworkregions of) a Nanobody® may be partially humanized or fully humanized.

In this respect, some preferred Nanobodies® of the invention areNanobodies® which specifically bind (as further defined herein) proteinF of hRSV and which:

-   i) are a humanized variant of the amino acid sequence with SEQ ID    NO: 5 (see Table A-1); and/or-   ii) have at least 80% amino acid identity with at least one of the    amino acid sequences of SEQ ID NO: 5 (see Table A-1) and/or at least    one of the amino acid sequences of SEQ ID NO's: 60-76, 138-141 and    146-157 (see Table A-4), in which for the purposes of determining    the degree of amino acid identity, the amino acid residues that form    the CDR sequences are disregarded;    and in which:-   iii) preferably one or more of the amino acid residues at positions    11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according to the Kabat    numbering are chosen from the Hallmark residues mentioned in Table    A-3 to Table A-8 of WO 08/020,079.

The present invention provides a number of humanized and/or sequenceoptimized amino acid sequences and/or Nanobodies® that are particularlysuited for binding protein F of hRSV. Therefore, in one aspect of thepresent invention, amino acid sequences and/or Nanobodies® are providedchosen from the following:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence and/or Nanobody® of theinvention comprises or essentially consists of one of SEQ ID NO's:60-76.

In another aspect, the present invention provides amino acid sequencesand/or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequences and/or Nanobodies® arechosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences and/or Nanobodies® of the inventioncomprise or essentially consist of one of SEQ ID NO's: 62, 65, 67, 68,75 and 76.

In yet another aspect, the present invention provides amino acidsequences and/or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequences and/or Nanobodies® arechosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferably, the amino acid sequence and/or Nanobody® of the inventioncomprises or essentially consists of SEQ ID NO: 65. In another preferredaspect, the amino acid sequence and/or Nanobody® of the inventioncomprises or essentially consists of SEQ ID NO: 76. In another preferredaspect, the amino acid sequence and/or Nanobody® of the inventioncomprises or essentially consists of SEQ ID NO: 76.

The present invention also provides a number of humanized and/orsequence optimized amino acid sequences and/or Nanobodies® that arechosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence and/or Nanobody® of theinvention comprises or essentially consists of one of SEQ ID NO's:146-153.

In another aspect, the present invention provides amino acid sequencesand/or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105;        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequences and/or Nanobodies® arechosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred amino acid sequences and/or Nanobodies® of the inventioncomprise or essentially consist of one of SEQ ID NO's: 146-149 and151-153.

The amino acid sequences and/or Nanobodies® of the present inventionshow reduced immunogenicity upon administration to a human subject. Inaddition, the amino acid sequences and/or Nanobodies® of the presentinvention show improved binding characteristics (suitably measuredand/or expressed as a K_(D)-value (actual or apparent), a K_(A)-value(actual or apparent), a k_(on)-rate and/or a k_(off)-rate, oralternatively as an IC₅₀ value, as further described herein) for proteinF of hRSV compared to their corresponding parental amino acid sequences(as described in PCT application PCT/EP2009/056975 entitled “Amino acidsequences directed against envelope proteins of a virus and polypeptidescomprising the same for the treatment of viral diseases” filed by AblynxN. V on 5 Jun. 2009).

During the production of the Nanobodies of the invention, a high levelof pyro glutamate (pGlu) on the amino terminus was detected by RP-HPLC.Levels of more than 15% pGlu were detected following fermentation andthe level of pGlu were steadily increasing upon storage during stabilitystudies. Such a modification leads to heterogeneity of the final productand needs to be avoided. The control/prevention of pGlu formation istherefore critical to keep therapeutic proteins within their setspecifications. Specific liquid formulations and/or storage conditionsare needed for proteins with an N-terminal Glutamic acid thus minimizingthe formation of pyro-Glutamic acid.

In the present invention, the possibility of pGlu post-translationalmodification of the N-terminus was eliminated by changing the N-terminalGlutamic acid (E) [HOOC—(CH2)2—protein] into an Aspartic acid (D)[HOOC—CH2—protein] which lead to increased product stability.Accordingly, the present invention also relates to amino acid sequencesand Nanobodies as described above wherein the Glutamic acid at position1 (said position determined according to Kabat numbering) is changedinto an Aspartic acid.

The present invention provides a number of sequence optimized amino acidsequences and/or Nanobodies® that show increased stability upon storageduring stability studies. Therefore, in one aspect of the presentinvention, amino acid sequences and/or Nanobodies® are provided chosenfrom the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the amino acid sequence and/or Nanobody® of theinvention comprises or essentially consists of one of SEQ ID NO's:138-141 and 154-157.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, whereinposition 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 62, whereinposition 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 65, whereinposition 1 (Glu) has been changed into Asp.

In another aspect, the amino add sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 76, whereinposition 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of one of SEQ ID NO's:146-153, wherein position 1 (Glu) has been changed into Asp.

Preferably, the amino acid sequence and/or Nanobody® of the inventioncomprises or essentially consists of SEQ ID NO: 138. In anotherpreferred aspect, the amino acid sequence and/or Nanobody® of theinvention comprises or essentially consists of SEQ ID NO: 139. Inanother preferred aspect, the amino acid sequence and/or Nanobody® ofthe invention comprises or essentially consists of SEQ ID NO: 140. Inanother preferred aspect, the amino acid sequence and/or Nanobody® ofthe invention comprises or essentially consists of SEQ ID NO: 141. Inanother preferred aspect, the amino acid sequence and/or Nanobody® ofthe invention comprises or essentially consists of one of SEQ ID NO's:154-157.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three, four, five, six, seven, eight, nine, ten,eleven or twelve) amino acid residues have been mutated selected fromthe following: Val5Leu, Ala14Pro, Ser19Arg, Ile20Leu, Glu44Gly,Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu andGly54Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three, four, five, six, seven, eight or nine)amino acid residues have been mutated selected from the following:Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three or four) amino acid residues have beenmutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leu andGln108Leu.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three, four, five, six or seven) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three, four, five, six, seven, eight, nine, ten,eleven or twelve) amino acid residues have been mutated selected fromthe following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, andwherein position 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three, four, five, six, seven, eight or nine)amino acid residues have been mutated selected from the following:Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, and wherein position 1 (Glu) has been changedinto Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three or four) amino acid residues have beenmutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leu andGln108Leu, and wherein position 1 (Glu) has been changed into Asp.

In another aspect, the amino acid sequences and/or Nanobodies® of theinvention comprise or essentially consist of SEQ ID NO: 5, wherein oneor more (such as two, three, four, five, six or seven) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu, andwherein position 1 (Glu) has been changed into Asp.

Preferably, the amino acid sequence and/or Nanobody® of the inventioncomprises or essentially consist of SEQ ID NO: 5, wherein followingamino acid residues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln;    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

The amino acid sequences and/or Nanobodies® of the present inventionshow improved properties such as e.g. improved stability, lessimmunogenicity, improved binding characteristics (suitably measuredand/or expressed as a K_(D)-value (actual or apparent), a K_(A)-value(actual or apparent), a k_(on)-rate and/or a k_(off)-rate, oralternatively as an IC₅₀ value, as further described herein), improvedaffinity and/or improved avidity for protein F of hRSV and/or improvedefficacy and/or potency for neutralizing hRSV compared to theircorresponding wild type amino acid sequences (as described in PCTapplication PCT/EP2009/056975 entitled “Amino acid sequences directedagainst envelope proteins of a virus and polypeptides comprising thesame for the treatment of viral diseases” filed by Ablynx N. V on 5 Jun.2009).

More in particular, the amino acid sequences and/or Nanobodies® of theinvention can bind to protein F of hRSV with an affinity (suitablymeasured and/or expressed as a K_(D)-value (actual or apparent), aK_(A)-value (actual or apparent), a k_(on)-rate and/or a k_(off)-rate,or alternatively as an IC₅₀ value, as further described herein)preferably such that they:

-   -   bind to protein F of hRSV with a dissociation constant (K_(D))        of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or less,        more preferably 15 nM to 1 nM or even 10 nM to 1 nM or less;        and/or such that they:    -   bind to protein F of hRSV with a k_(on)-rate of between 10⁴ M⁻¹        s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹ s⁻¹ and 10⁷        M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more;        and/or such that they:    -   bind to protein F of hRSV with a k_(off) rate between 10⁻² s⁻¹        (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near irreversible        complex with a t_(1/2) of multiple days), preferably between        10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower;

Some preferred IC50 values for binding of the amino acid sequences ofthe invention to protein F of hRSV will become clear from the furtherdescription and examples herein.

Assays to determine the IC50 include competition assays such ascompetition ELISA (e.g. competition with Synagis® or its Fab fragment)or more preferably neutralization assays such as the microneutraiizationassay described by Anderson et al. (1985, J. Olin. Microbiol. 22:1050-1052; 1988, J. Virol. 62: 4232-4238), modifications of this assaysuch as e.g. described in Example 6, or a plaque reduction assay as forexample described by Johnson et al. (1997, J. Inf. Dis. 176: 1215-1224),and modifications thereof.

For example, in a competition assay with the Fab fragment of Synagis®,the amino acid sequences of the invention may have IC50 values between 1nM and 100 nM, preferably between 10 nM and 50 nM, or less.

For example, in a microneutralization assay on hRSV Long (such as e.g.described in Example 6) the amino acid sequences of the invention mayhave IC50 values between 100 nM and 1000 nM, preferably between 100 nMand 500 nM, or less.

The amino acid sequences and Nanobodies® provided by the invention arepreferably in essentially isolated form (as defined herein), or formpart of a polypeptide of the invention (also referred to as “polypeptideof the invention” or “construct of the invention”; both are usedinterchangeably), which may comprise or essentially consist of one ormore amino acid sequences or Nanobodies® of the invention and which mayoptionally further comprise one or more further amino acid sequences orNanobodies® (all optionally linked via one or more suitable linkers).

Accordingly, in another aspect, the invention relates to a polypeptide(also referred to herein as a “polypeptide of the invention”) thatcomprises or essentially consists of one or more amino acid sequences orNanobodies® of the invention (or suitable fragments thereof).

The process of designing/selecting and/or preparing a polypeptide of theinvention, starting from an amino acid sequence or Nanobody® of theinvention, is also referred to herein as “formatting” said amino acidsequence or Nanobody® of the invention; and an amino acid sequence orNanobody® of the invention that is made part of a polypeptide of theinvention is said to be “formatted” or to be “in the format of” saidpolypeptide of the invention. Examples of ways in which an amino acidsequence or Nanobody® of the invention can be formatted and examples ofsuch formats will be clear to the skilled person based on the disclosureherein; and such formatted amino acid sequences or Nanobodies® form afurther aspect of the invention.

For example, and without limitation, the one or more amino acidsequences or Nanobodies® of the invention may be used as a binding unitin such a polypeptide, which may optionally contain one or more furtheramino add sequences that can serve as a binding unit (i.e. against thesame or another epitope on protein F of hRSV and/or against one or moreother antigens, proteins or targets than protein F of hRSV), so as toprovide a monovalent, multivalent, multiparatopic or multispecificpolypeptide of the invention, respectively, all as described herein. Thepresent invention thus also relates to a polypeptide which is amonovalent polypeptide or construct comprising or essentially consistingof an amino acid sequence or Nanobody® of the invention. The presentinvention thus also relates to a polypeptide which is a multivalentpolypeptide or construct, such as e.g. a bivalent or trivalentpolypeptide or construct. The present invention also relates to apolypeptide which is a multispecific polypeptide or construct, such ase.g. a bispecific or trispecific polypeptide or construct. The presentinvention also relates to a polypeptide which is a multiparatopicpolypeptide or construct, such as e.g. a bisparatopic or triparatopicpolypeptide or construct.

Accordingly, in a preferred, but non-limiting aspect, the amino acidsequence or Nanobody® of the invention comprises at least one furtheramino acid sequence or Nanobody®, so as to provide a polypeptide of theinvention that comprises at least two, such as two, three, four, five ormore amino acid sequences or Nanobodies®, in which said amino acidsequences or Nanobodies® may optionally be linked via one or more linkersequences (as defined herein). Polypeptides of the invention thatcomprise two or more amino acid sequences or Nanobodies®, of which atleast one, and preferably all, is/are an amino acid sequence orNanobody® of the invention, will also be referred to herein as“multivalent” polypeptides of the invention, and the amino acidsequences or Nanobodies® present in such polypeptides will also bereferred to herein as being in a “multivalent format”. For example a“bivalent” polypeptide of the invention comprises two amino acidsequences and/or Nanobodies®, optionally linked via a linker sequence,whereas a “trivalent” polypeptide of the invention comprises three aminoacid sequences and/or Nanobodies®, optionally linked via two linkersequences; etc.; in which at least one of the amino acid sequencesand/or Nanobodies® present in the polypeptide, and up to all of theamino acid sequences and/or Nanobodies® present in the polypeptide,is/are a amino acid sequences and/or Nanobodies® of the invention.

In a multivalent polypeptide of the invention, the two or more aminoacid sequences or Nanobodies® may be the same or different, and may bedirected against the same antigen or antigenic determinant (for exampleagainst the same part(s) or epitope(s) or against different parts orepitopes) or may alternatively be directed against different antigens orantigenic determinants; or any suitable combination thereof. Forexample, a bivalent polypeptide of the invention may comprise (a) twoidentical amino acid sequences or Nanobodies®; (b) a first amino acidsequence or Nanobody® directed against a first antigenic determinant ofa protein or antigen and a second amino acid sequence or Nanobody®directed against the same antigenic determinant of said protein orantigen which is different from the first amino acid sequence orNanobody®; (c) a first amino acid sequence or Nanobody® directed againsta first antigenic determinant of a protein or antigen and a second aminoacid sequence or Nanobody® directed against another antigenicdeterminant of said protein or antigen; or (d) a first amino acidsequence or Nanobody® directed against a first protein or antigen and asecond amino acid sequence or Nanobody® directed against a secondprotein or antigen (i.e. different from said first antigen). Similarly,a trivalent polypeptide of the invention may, for example and withoutbeing limited thereto, comprise (a) three identical amino acid sequencesor Nanobodies®; (b) two identical amino acid sequences or Nanobody®against a first antigenic determinant of an antigen and a third aminoacid sequence or Nanobody® directed against a different antigenicdeterminant of the same antigen; (c) two identical amino acid sequencesor Nanobodies® against a first antigenic determinant of an antigen and athird amino acid sequence or Nanobody® directed against a second antigendifferent from said first antigen; (d) a first amino acid sequence orNanobody® directed against a first antigenic determinant of a firstantigen, a second amino acid sequence or Nanobody® directed against asecond antigenic determinant of said first antigen and a third aminoacid sequence or Nanobody® directed against a second antigen differentfrom said first antigen; or (e) a first amino acid sequence or Nanobody®directed against a first antigen, a second amino acid sequence orNanobody® directed against a second antigen different from said firstantigen, and a third amino acid sequence or Nanobody® directed against athird antigen different from said first and second antigen.

In a preferred aspect, the invention provides a multivalent, preferablya bivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) amino acid sequences orNanobodies® of the invention (as described above).

In one aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) or at least three (preferablyidentical) amino acid sequences or Nanobodies® chosen from amino acidsequences that comprise at least a stretch of amino acid residues chosenfrom the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

In another aspect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) or at least three (preferablyidentical) amino acid sequences or Nanobodies® chosen from amino acidsequences that comprise two or more stretches of amino acid residues inwhich one stretch is chosen from the following:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a), and b) should always be present in the amino acid        sequence that forms part of the multivalent polypeptide and such        that the second stretch of amino acid residues is chosen from        one of c), d), e) and f).

Preferred multivalent (such as bivalent or trivalent) polypeptides maycomprise or essentially consist of at least two (preferably identical)or at least three (preferably identical) amino acid sequences orNanobodies® chosen from amino acid sequences that comprise three or morestretches of amino acid residues, in which the first stretch of aminoacid residues is chosen from the group consisting of:

-   -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;        the second stretch of amino acid residues is chosen from the        group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein of hRSV with the same, about the            same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;            and the third stretch of amino acid residues is chosen from            the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino add residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

In yet another aspect, the invention provides a multivalent, preferablya bivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) or at least three (preferablyidentical) amino acid sequences or Nanobodies® that essentially consistof 4 framework regions (FR1 to FR4, respectively) and 3 complementaritydetermining regions (CDR1 to CDR3, respectively), in which CDR2 ischosen from:

-   -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein of hRSV with the same, about the            same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

In yet another aspect, the invention provides a multivalent, preferablya bivalent or trivalent polypeptide comprising or essentially consistingof at least two (preferably identical) or at least three (preferablyidentical) amino acid sequences or Nanobodies® that essentially consistof 4 framework regions (FR1 to FR4, respectively) and 3 complementaritydetermining regions (CDR1 to CDR3, respectively), in which CDR2 ischosen from the group consisting of:

-   -   a) SEQ ID NO: 102; or    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one of CDR1 or CDR3 is chosen from:        -   CDR1 chosen from the group consisting of:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;        -   CDR3 chosen from the group consisting of:    -   e) SEQ ID NO: 121; or    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Preferably, multivalent (such as bivalent or trivalent) polypeptides maycomprise or essentially consist of at least two (preferably identical)or at least three (preferably identical) amino acid sequences orNanobodies® that essentially consist of 4 framework regions (FR1 to FR4,respectively) and 3 complementarity determining regions (CDR1 to CDR3,respectively), in which:

-   -   CDR1 is chosen from the group consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and        -   CDR2 is chosen from the group consisting of:    -   c) SEQ ID NO: 102; or    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference; and        -   CDR3 is chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

In a specific aspect, the multivalent (such as bivalent or trivalent)polypeptides may comprise or essentially consist of at least two(preferably identical) or at least three (preferably identical) aminoacid sequences or Nanobodies® that comprise at least SEQ ID NO: 102.

In another specific aspect, the multivalent (such as bivalent ortrivalent) polypeptides may comprise or essentially consist of at leasttwo (preferably identical) or at least three (preferably identical)amino acid sequences or Nanobodies® that comprise at least SEQ ID NO:102 and at least one stretch of amino acid residues (CDR sequence)chosen from:

-   -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

Preferred multivalent (such as bivalent or trivalent) polypeptides maycomprise or essentially consist of at least two (preferably identical)or at least three (preferably identical) amino acid sequences orNanobodies® that comprise at least SEQ ID NO: 102 and at least twostretches of amino acid residues (CDR sequences) in which one stretch ischosen from the group consisting of the stretches of amino acid residuesdefined in c) and d) and in which the other stretch is chosen from thegroup consisting of the stretches of amino acid residues defined in e)and f).

In a specific aspect, the multivalent (such as bivalent or trivalent)polypeptides may comprise or essentially consist of at least two(preferably identical) or at least three (preferably identical) aminoacid sequences or Nanobodies® that comprise at least SEQ ID NO: 102 andat least one stretch of amino acid residues (CDR sequence) chosen fromSEQ ID NO: 98 and SEQ ID NO: 121; or amino acid sequences or Nanobodies®that comprise at least SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® of the invention (as described above). In another preferredaspect, the invention provides a bivalent polypeptide comprising oressentially consisting of two (preferably identical) amino acidsequences or Nanobodies® of the invention (as described above). Inanother preferred aspect, the invention provides a trivalent polypeptidecomprising or essentially consisting of three (preferably identical)amino acid sequences or Nanobodies® of the invention (as describedabove).

The invention also provides a multivalent, preferably a bivalent ortrivalent polypeptide comprising or essentially consisting of at leasttwo (preferably identical) amino acid sequences or Nanobodies® chosenfrom the following:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 60-76.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino add sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68, 75 and76.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from SEQ ID NO's: 65 and 76.

The invention also provides a multivalent, preferably a bivalent ortrivalent polypeptide comprising or essentially consisting of at leasttwo (preferably identical) amino acid sequences or Nanobodies® chosenfrom the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least two identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 146-153.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105;        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentiallyconsists of at least two identical amino acid sequences or Nanobodies®chosen from SEQ ID NO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three, four, five, six, seven, eight,nine, ten, eleven or twelve) amino acid residues have been mutatedselected from the following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu,Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leuand Gly54Asp.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three, four, five, six, seven, eight ornine) amino acid residues have been mutated selected from the following:Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three or four) amino acid residues havebeen mutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leuand Gln108Leu.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three, four, five, six or seven) aminoacid residues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least two (preferably identical) amino acid sequencesor Nanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich following amino acid residues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 50-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 60-76.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 62, 65, 67, 68, 75 and76.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 65 and 76.

The invention also provides a multivalent, preferably a trivalentpolypeptide comprising or essentially consisting of at least three(preferably identical) amino acid sequences or Nanobodies® chosen fromthe following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least three identical amino acid sequencesor Nanobodies® chosen from one of SEQ ID NO's: 146-153.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino add difference        with one of SEQ ID NO's: 146-149 and 151-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105;        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentiallyconsists of at least three identical amino acid sequences or Nanobodies®chosen from SEQ ID NO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three, four, five, six, seven, eight,nine, ten, eleven or twelve) amino acid residues have been mutatedselected from the following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu,Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leuand Gly54Asp.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three, four, five, six, seven, eight ornine) amino acid residues have been mutated selected from the following:Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three or four) amino acid residues havebeen mutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leuand Gln108Leu.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich one or more (such as two, three, four, five, six or seven) aminoacid residues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu.

In another preferred aspect, the invention provides a multivalent,preferably a trivalent polypeptide comprising or essentially consistingof at least three (preferably identical) amino acid sequences orNanobodies® that comprise or essentially consist of SEQ ID NO: 5, inwhich following amino acid residues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

The invention also provides a multivalent, preferably a bivalent ortrivalent polypeptide as described above in which the Glutamic acid atposition 1 has been changed into an Aspartic acid.

In this respect, the invention provides a multivalent, preferably abivalent or trivalent polypeptide comprising or essentially consistingof at least one amino acid sequence or Nanobody® chosen from thefollowing:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino add sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least one amino add sequence or Nanobody®chosen from one of SEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 5, in which the Glutamicacid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 62, in which theGlutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 65, in which theGlutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 76, in which theGlutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 75, in which theGlutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 147, in which theGlutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 149, in which theGlutamic acid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or that comprises oressentially consists of SEQ ID NO: 153, in which the Glutamic acid atposition 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 5, in which one or more(such as two, three, four, five, six, seven, eight, nine, ten, eleven ortwelve) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, andwherein the Glutamic acid at position 1 has been changed into Asparticacid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 5, in which one or more(such as two, three, four, five, six, seven, eight or nine) amino acidresidues have been mutated selected from the following: Val5Leu,Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leuand Gly54Asp, and wherein the Glutamic acid at position 1 has beenchanged into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 5, in which one or more(such as two, three or four) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu,and wherein the Glutamic acid at position 1 has been changed intoAspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 5, in which one or more(such as two, three, four, five, six or seven) amino acid residues havebeen mutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leu,Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu, and wherein the Glutamicacid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a multivalent,preferably a bivalent or trivalent polypeptide comprising or essentiallyconsisting of at least one amino acid sequence or Nanobody® thatcomprises or essentially consists of SEQ ID NO: 5, in which followingamino acid residues have been mutated:

-   -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is abivalent polypeptide and comprises or essentially consists of twoidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 60-76.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is abivalent polypeptide and comprises or essentially consists of twoidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is abivalent polypeptide and comprises or essentially consists of twoidentical amino acid sequences or Nanobodies® chosen from SEQ ID NO's:65 and 76.

The invention also provides a bivalent polypeptide comprising oressentially consisting of two (preferably identical) amino acidsequences or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, 14 at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is abivalent polypeptide and comprises or essentially consists of twoidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 146-153.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105;        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention a bivalent polypeptidecomprising or essentially consisting of two (preferably identical) aminoacid sequences or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentiallyconsists of two amino acid sequences or Nanobodies® chosen from SEQ IDNO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight, nine, ten, eleven or twelve) aminoacid residues have been mutated selected from the following: Val5Leu,Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight or nine) amino acid residues havebeen mutated selected from the following: Val5Leu, Ala14Pro, Glu44Gly,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three or four) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six or seven) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,Asp85Glu, Arg105Gln and Gln108Leu.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of two (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which following amino acidresidues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

The invention also provides a bivalent polypeptide as described above inwhich the Glutamic acid at position 1 has been changed into an Asparticacid.

In this respect, the invention also provides a bivalent polypeptidecomprising or essentially consisting of at least one amino acid sequenceor Nanobody® chosen from the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least one amino acid sequence or Nanobody®chosen from one of SEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which the Glutamic acid at position 1 has been changed intoAspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 62, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 65, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 76, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 75, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 147, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 149, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 153, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three, four, five, six,seven, eight, nine, ten, eleven or twelve) amino acid residues have beenmutated selected from the following: Val5Leu, Ala14Pro, Ser19R,Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, and wherein the Glutamic acid at position 1 hasbeen changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three, four, five, six,seven, eight or nine) amino acid residues have been mutated selectedfrom the following: Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein the Glutamicacid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three or four) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu and Gln108Leu, and wherein the Glutamic acid atposition 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three, four, five, six orseven) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Glnand Gln108Leu, and wherein the Glutamic acid at position 1 has beenchanged into Aspartic acid.

In another preferred aspect, the invention provides a bivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which following amino acid residues have been mutated:

-   -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is atrivalent polypeptide and comprises or essentially consists of threeidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 60-76.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is atrivalent polypeptide and comprises or essentially consists of threeidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is atrivalent polypeptide and comprises or essentially consists of threeidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 65 and 76.

The invention also provides a trivalent polypeptide comprising oressentially consisting of three (preferably identical) amino acidsequences or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention is atrivalent polypeptide and comprises or essentially consists of threeidentical amino acid sequences or Nanobodies® chosen from one of SEQ IDNO's: 146-153.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105;        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention a trivalent polypeptidecomprising or essentially consisting of three (preferably identical)amino acid sequences or Nanobodies® chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino add sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

Preferred polypeptides of the invention comprises or essentiallyconsists of three amino acid sequences or Nanobodies® chosen from SEQ IDNO's: 146-149 and 151-153.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight, nine, ten, eleven or twelve) aminoacid residues have been mutated selected from the following: Val5Leu,Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight or nine) amino acid residues havebeen mutated selected from the following: Val5Leu, Ala14Pro, Glu44Gly,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three or four) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six or seven) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,Asp85Glu, Arg105Gln and Gln108Leu.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of three (preferablyidentical) amino acid sequences or Nanobodies® that comprise oressentially consist of SEQ ID NO: 5, in which following amino acidresidues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu; Gly78Leu, Ala83Arg,        Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

A preferred multivalent polypeptide of the invention comprises oressentially consists of three amino add sequences or Nanobodies® withSEQ ID NO: 62. Another preferred multivalent polypeptide of theinvention comprises or essentially consists of three amino acidsequences or Nanobodies® with SEQ ID NO: 65. Another preferredmultivalent polypeptide of the invention comprises or essentiallyconsists of three amino acid sequences or Nanobodies® with SEQ ID NO:76. Another preferred multivalent polypeptide of the invention comprisesor essentially consists of three amino acid sequences or Nanobodies®with SEQ ID NO: 75. Another preferred multivalent polypeptide of theinvention comprises or essentially consists of three amino acidsequences or Nanobodies® with SEQ ID NO: 147. Another preferredmultivalent polypeptide of the invention comprises or essentiallyconsists of three amino acid sequences or Nanobodies® with SEQ ID NO:149. Another preferred multivalent polypeptide of the inventioncomprises or essentially consists of three amino acid sequences orNanobodies® with SEQ ID NO: 153.

The invention also provides a trivalent polypeptide as described abovein which the Glutamic acid at position 1 has been changed into anAspartic acid.

In this respect, the invention also provides a trivalent polypeptidecomprising or essentially consisting of at least one amino acid sequenceor Nanobody® chosen from the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the polypeptide of the invention comprisesor essentially consists of at least one amino acid sequence or Nanobody®chosen from one of SEQ ID NO's: 138-141 and 154-157.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which the Glutamic acid at position 1 has been changed intoAspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 62, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 65, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 76, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 75, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 147, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 149, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 153, in which the Glutamic acid at position 1 has been changedinto Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three, four, five, six,seven, eight, nine, ten, eleven or twelve) amino acid residues have beenmutated selected from the following: Val5Leu, Ala14Pro, Ser19R,Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, and wherein the Glutamic acid at position 1 hasbeen changed into Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three, four, five, six,seven, eight or nine) amino acid residues have been mutated selectedfrom the following: Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein the Glutamicacid at position 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three or four) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu and Gln108Leu, and wherein the Glutamic acid atposition 1 has been changed into Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which one or more (such as two, three, four, five, six orseven) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Glnand Gln108Leu, and wherein the Glutamic acid at position 1 has beenchanged into Aspartic acid.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of at least one aminoacid sequence or Nanobody® that comprises or essentially consists of SEQID NO: 5, in which following amino acid residues have been mutated:

-   -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and    -   Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 77-79 and 158;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 77-79 and 158, provided that:        -   i) the amino acid sequences or Nanobodies® encompassed in            said polypeptide have a Glutamine (Gln, Q) at position 105,            a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at            position 83 and/or a Glutamic acid (Glu, E) at position 85            (said positions determined according to Kabat numbering);            and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the invention provides a trivalent polypeptidechosen from the following polypeptides:

-   -   a) SEQ ID NO is: 77-79 and 158;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 77-79 and 158, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Glutamine (Gln, Q) at position 105, a            Leucine (Leu, L) at position 78, an Arginine (Arg, R) at            position 83 and a Glutamic acid (Glu, E) at position 85            (said positions determined according to Kabat numbering);            and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of one of SEQ ID NO's: 77-79 and 158.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO: 78 and 79;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 78 and 79, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has an Aspartic acid (Asp, D) at position 54, a            Glutamine (Gln, Q) at position 105, a Leucine (Leu, L) at            position 78, an Arginine (Arg, R) at position 83 and/or a            Glutamic acid (Glu, E) at position 85 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

In a preferred aspect, the invention provides a trivalent polypeptidechosen from the following polypeptides:

-   -   a) SEQ ID NO: 78 and 79; or    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 78 and 79, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has an Aspartic acid (Asp, D) at position 54, a            Glutamine (Gln, Q) at position 105, a Leucine (Leu, L) at            position 78, an Arginine (Arg, R) at position 83 and a            Glutamic acid (Glu, E) at position 85 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

A preferred trivalent polypeptide of the invention comprises oressentially consists of SEQ ID NO: 78. Another preferred trivalentpolypeptide of the invention comprises or essentially consists of SEQ IDNO: 79.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Proline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20            and/or Leucine (Leu, L) at position 108 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of one of SEQ ID NO's: 159-161.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Praline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20            and/or Leucine (Leu, L) at position 108; and in addition            Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at            position 85 and/or Glutamine (Gln, Q) at position 105 (said            positions determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

In another preferred aspect, the invention provides a trivalentpolypeptide chosen from the following polypeptides:

-   -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Proline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20            and/or Leucine (Leu, L) at position 108 and in addition            Arginine (Arg, R) at position 83, Glutamic acid (Glu, E) at            position 85 and/or Glutamine (Gln, Q) at position 105 so            that when the polypeptide has no more than 3, preferably no            more than 2, more preferably no more than 1 amino acid            difference with:            -   SEQ ID NO: 159, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83 and Glutamine (Gln, Q) at                position 105;            -   SEQ ID NO: 160, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83, Glutamic add (Glu, E) at                position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 161, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83 and Glutamic acid (Glu, E) at                position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

Preferred trivalent polypeptides of the invention comprise oressentially consist of one of SEQ ID NO's: 159-161.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three, four, five, six, seven, eight, nine, ten, eleven ortwelve) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three, four, five, six, seven, eight or nine) amino acidresidues have been mutated selected from the following: Val5Leu,Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leuand Gly54Asp.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three or four) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three, four, five, six or seven) amino acid residues havebeen mutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leu,Ala83Arg, Asp85Glu, Arg105Gln and Gln108Le.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, followingamino acid residues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

In another preferred aspect, the polypeptide of the inventionessentially consists of the amino add sequence of SEQ ID NO: 77. Inanother preferred aspect, the polypeptide of the invention essentiallyconsists of the amino acid sequence of SEQ ID NO: 78. In anotherpreferred aspect, the polypeptide of the invention essentially consistsof the amino acid sequence of SEQ ID NO: 79. In another preferredaspect, the polypeptide of the invention essentially consists of one ofSEQ ID NO's: 158-161.

During the production of the polypeptides of the invention, a high levelof pyro glutamate (pGlu) on the amino terminus was detected by RP-HPLC.Levels of more than 15% pGlu were detected following fermentation andthe levels of pGlu were steadily increasing upon storage duringstability studies. Such a modification leads to heterogeneity of thefinal product and needs to be avoided. The control/prevention of pGluformation is therefore critical to keep therapeutic proteins withintheir set specifications. Specific liquid formulations and/or storageconditions are needed for proteins with an N-terminal Glutamic acid thusminimizing the formation of pyro-Glutamic acid.

In the present invention, the possibility of pGlu post-translationalmodification of the N-terminus was eliminated by changing the N-terminalGlutamic acid (E) [HOOC—(CH2)2—protein] into an Aspartic acid (D)[HOOC—CH2—protein] which lead to increased product stability.Accordingly, the present invention also relates to polypeptides asdescribed above wherein the Glutamic acid at position 1 is changed intoan Aspartic acid.

The present invention provides a number of sequence optimizedpolypeptides that show increased stability upon storage during stabilitystudies. Accordingly, the invention provides a trivalent polypeptide asdescribed above, wherein the first amino acid (Glutamic acid) has beenchanged into Aspartic acid.

In one aspect, the invention provides a trivalent polypeptide chosenfrom the following polypeptides:

-   -   a) SEQ ID NO's: 142-145 and 162-165;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 142-145 and 162-165, provided that:        -   i) the first amino acid sequence or Nanobody® encompassed in            said polypeptide has an Aspartic acid (Asp, D) at position            1; and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

A preferred trivalent polypeptide of the invention comprises oressentially consists of SEQ ID NO: 142. Another preferred trivalentpolypeptide of the invention comprises or essentially consists of SEQ IDNO: 143. Another preferred trivalent polypeptide of the inventioncomprises or essentially consists of SEQ ID NO: 144. Another preferredtrivalent polypeptide of the invention comprises or essentially consistsof SEQ ID NO: 145. Another preferred trivalent polypeptide of theinvention comprises or essentially consists of one of SEQ ID NO's:162-165.

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 77, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 78, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 79, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 158, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 159, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 160, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 161, inwhich the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three, four, five, six, seven, eight, nine, ten, eleven ortwelve) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, andwherein the Glutamic acid at position 1 has been changed into Asparticacid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three, four, five, six, seven, eight or nine) amino acidresidues have been mutated selected from the following: Val5Leu,Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leuand Gly54Asp, and wherein the Glutamic acid at position 1 has beenchanged into Aspartic acid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three or four) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu,and wherein the Glutamic acid at position 1 has been changed intoAspartic acid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, one or more(such as two, three, four, five, six or seven) amino acid residues havebeen mutated selected from the following: Ala14Pro, Ser19Arg, Ile20Leu,Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu, and wherein the Glutamicacid at position 1 has been changed into Aspartic acid (Glu1Asp).

In another preferred aspect, the invention provides a trivalentpolypeptide comprising or essentially consisting of SEQ ID NO: 53, inwhich in at least one (preferably in two, more preferably in all three)Nanobody®/Nanobodies® that form(s) part of SEQ ID NO: 53, followingamino acid residues have been mutated:

-   -   Glu1Asp    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

In another preferred aspect, the polypeptide of the inventionessentially consists of the amino acid sequence of SEQ ID NO: 142. Inanother preferred aspect, the polypeptide of the invention essentiallyconsists of the amino acid sequence of SEQ ID NO: 143. In anotherpreferred aspect, the polypeptide of the invention essentially consistsof the amino acid sequence of SEQ ID NO: 144. In another preferredaspect, the polypeptide of the invention essentially consists of theamino acid sequence of SEQ ID NO: 145. In another preferred aspect, thepolypeptide of the invention essentially consists of one of SEQ ID NO's:162-165.

Polypeptides with the amino acid sequences and polypeptide sequences asdescribed above have shown advantageous properties for use asprophylactic, therapeutic and/or pharmacologically active agents such ase.g. improved stability, less immunogenicity, improved bindingcharacteristics (suitably measured and/or expressed as a K_(D)-value(actual or apparent), a K_(A)-value (actual or apparent), a k_(on)-rateand/or a k_(off)-rate, or alternatively as an IC₅₀ value, as furtherdescribed herein), improved affinity and/or improved avidity for proteinF of hRSV and/or improved efficacy and/or potency for neutralizing hRSV.

More in particular, these polypeptides and compounds of the inventioncan bind to protein F of hRSV with an affinity (suitably measured and/orexpressed as a K_(D)-value (actual or apparent), a K_(A)-value (actualor apparent), a k_(on)-rate and/or a k_(off)-rate, or alternatively asan IC₅₀ value, as further described herein) preferably such that they:

-   -   bind to protein F of hRSV with a dissociation constant (K_(D))        of 100 nM to 0.1 nM or less, preferably 10 nM to 0.1 nM or less,        more preferably 1 nM to 0.1 nM or less;        and/or such that they:    -   bind to protein F of hRSV with a k_(on)-rate of between 10⁴        M⁻¹S⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹ s⁻¹ and        10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more;        and/or such that they:    -   bind to protein F of hRSV with a k_(off) rate between 10⁻² s⁻¹        (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near irreversible        complex with a t_(1/2) of multiple days), preferably between        10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, more preferably between 5×10⁻³ s⁻¹ and        10⁻⁴ s⁻¹, or lower;

Some preferred IC50 values for binding of the polypeptides of theinvention to protein F of hRSV will become clear from the furtherdescription and examples herein.

Assays to determine the IC50 include competition assays such ascompetition ELISA (e.g. competition with Synagis® or its Fab fragment)or more preferably neutralization assays such as the microneutralizationassay described by Anderson et al. (1985, J. Clin. Microbiol. 22:1050-1052), modification of this assay as described in example 6, or aplaque reduction assay as described by Johnson et al. (1997, J. Inf.Dis. 176: 1215-1224), and modifications thereof.

For example, in a competition assay with Synagis®, the polypeptides ofthe invention may have IC50 values between 1 nM and 100 nM, preferablybetween 10 nM and 50 nM, or less.

For example, in a microneutralization assay of RSV strain Long (such ase.g. described in Example 6) the polypeptides of the invention may haveIC50 values between 10 pM and 1000 pM, preferably between 10 pM and 250pM, more preferably between 50 pM and 200 pM or less. In amicroneutralization assay, the polypeptides of the invention may haveIC50 values that are at least the same and preferably better, at leastten times better, preferably twenty times better, more preferably fiftytimes better, even more preferably sixty, seventy, eighty or more timesbetter compared to the IC50 value obtained with Synagis®.

The invention also relates to a monovalent polypeptide or construct(also referred to as “monovalent polypeptide of the invention” or“monovalent construct of the invention”), comprising or essentiallyconsisting of one amino acid sequence or Nanobody® of the invention.Preferred monovalent constructs of the invention comprise or essentiallyconsist of one of SEQ ID NO's: 60-76, such as one of SEQ ID NO's: 62,65, 67, 68, 75 and 76, such as e.g. SEQ ID NO's: 65 or 75; one of SEQ IDNO's: 138-141; one of SEQ ID NO's: 146-153; or one of SEQ ID NO's:154-157. Such a monovalent constructs, as well as the amino acidsequences and Nanobodies® of the invention can be used for thepreparation of a polypeptide of the invention, such as e.g. themultivalent polypeptides of the invention described above.

The polypeptides of the invention can generally be prepared by a methodwhich comprises at least the step of suitably linking the amino acidsequence, Nanobody® or monovalent construct of the invention to one ormore further amino acid sequences, Nanobodies® or monovalent constructsof the invention, optionally via the one or more suitable linkers, so asto provide the polypeptide of the invention. Polypeptides of theinvention can also be prepared by a method which generally comprises atleast the steps of providing a nucleic acid that encodes a polypeptideof the invention, expressing said nucleic acid in a suitable manner, andrecovering the expressed polypeptide of the invention. Such methods canbe performed in a manner known per se, which will be clear to theskilled person, for example on the basis of the methods and techniquesfurther described herein.

A method for preparing multivalent, multiparatopic and/or multispecificamino acids or polypeptides of the invention may comprise at least thesteps of linking two or more monovalent amino acid sequences ormonovalent constructs of the invention and for example one or morelinkers together in a suitable manner. The monovalent constructs (andlinkers) can be coupled by any method known in the art and as furtherdescribed herein. Preferred techniques include the linking of thenucleic acid sequences that encode the monovalent constructs (andlinkers) to prepare a genetic construct that expresses the multivalent,multiparatopic and/or multispecific amino acid sequence or polypeptide.Techniques for linking amino acid sequences or nucleic acid sequenceswill be clear to the skilled person, and reference is again made to thestandard handbooks, such as Sambrook et al. and Ausubel et al.,mentioned above, as well as the Examples below.

Accordingly, the present invention also relates to the use of an aminoacid sequence, a Nanobody® or a monovalent construct of the invention inpreparing a multivalent polypeptide of the invention. The method for thepreparation of a multivalent polypeptide will comprise the linking of anamino acid sequence, a Nanobody® or a monovalent construct of theinvention to at least one further amino acid sequence, Nanobody® ormonovalent construct of the invention, optionally via one or morelinkers. The amino acid sequence, Nanobody® or monovalent construct isthen used as a binding domain or binding unit in providing and/orpreparing the multivalent polypeptide comprising two (e.g. in a bivalentpolypeptide), three (e.g. in a trivalent polypeptide) or more (e.g. in amultivalent polypeptide) binding units. In this respect, the amino acidsequence, Nanobody® and monovalent construct may be used as a bindingdomain or binding unit in providing and/or preparing a multivalent andpreferably bivalent or trivalent polypeptide of the invention comprisingtwo, three or more binding units. Preferably, the binding domains orbinding units are linked via a linker such that the multivalentpolypeptide preferably exhibits intramolecular binding compared tointermolecular binding. Also preferably the multivalent polypeptide cansimultaneously bind both or all three binding sites on the F protein ofRSV.

Accordingly, the present invention also relates to the use of an aminoacid sequence or a Nanobody® of the invention (as described above) inpreparing a multivalent polypeptide. The method for the preparation ofthe multivalent polypeptide will comprise the linking of the amino acidsequence or Nanobody® of the invention to at least one further aminoacid sequences or Nanobody® of the invention, optionally via one or morelinkers.

In a preferred aspect, the present invention relates to the use of anamino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing amultivalent polypeptide comprises or essentially consists of one of SEQID NO's: 60-76.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or a            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; or    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino add difference        with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76, provided        that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing amultivalent polypeptide comprises or essentially consists of one of SEQID NO: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino add difference        with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing amultivalent polypeptide comprises or essentially consists of SEQ ID NO:65. In another preferred aspect, the amino acid sequence used inpreparing a multivalent polypeptide comprises or essentially consists ofSEQ ID NO: 76.

In a preferred aspect, the present invention relates to the use of anamino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing amultivalent polypeptide comprises or essentially consists of one of SEQID NO's: 146-153.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the following:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing amultivalent polypeptide comprises or essentially consists of one of SEQID NO's: 146-149 and 151-153.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine, ten, eleven or twelve) amino acid residues have beenmutated selected from the following: Val5Leu, Ala14Pro, Ser19R,Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,Arg105Gln, Gln108Leu and Gly54Asp, in preparing a multivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three or four) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu and Gln108Leu, in preparing a multivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six orseven) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Glnand Gln108Leu, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which following amino acid residues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and    -   Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,        in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the above wherein the amino acid(Glutamic acid) at position I has been changed into Aspartic acid, inpreparing a multivalent polypeptide.

In this respect, the present invention relates to the use of an aminoacid sequence chosen from the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a multivalent polypeptide. The method for the            preparation of the multivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing amultivalent polypeptide comprises or essentially consists of SEQ ID NO:138. In another preferred aspect, the amino acid sequence used inpreparing a multivalent polypeptide comprises or essentially consists ofSEQ ID NO: 139. In another preferred aspect, the amino acid sequenceused in preparing a multivalent polypeptide comprises or essentiallyconsists of SEQ ID NO: 140. In another preferred aspect, the amino acidsequence used in preparing a multivalent polypeptide comprises oressentially consists of SEQ ID NO: 141. In another preferred aspect, theamino acid sequence used in preparing a multivalent polypeptidecomprises or essentially consists of one of SEQ ID NO's: 154-157.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 62, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 65, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 76, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 75, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 147, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 149, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 153, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine, ten, eleven or twelve) amino acid residues have beenmutated selected from the following: Val5Leu, Ala14Pro, Ser19R,Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, and wherein Glutamic acid at position 1 has beenchanged into Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,Arg105Gln, Gln108Leu and Gly54Asp, and wherein Glutamic acid at position1 has been changed into Aspartic acid, in preparing a multivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three or four) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu and Gln108Leu, and wherein Glutamic acid at position1 has been changed into Aspartic acid, in preparing a multivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six orseven) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Glnand Gln108Leu, and wherein Glutamic acid at position 1 has been changedinto Aspartic acid, in preparing a multivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which following amino acid residues have been mutated:

-   -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln,        in preparing a multivalent polypeptide.

The present invention also relates to the use of two amino acidsequences and/or Nanobodies® of the invention (as described above) inpreparing a bivalent polypeptide. The method for the preparation of thebivalent polypeptide will comprise the linking of the amino acidsequences and/or Nanobodies® of the invention, optionally via a linker.

Accordingly, in a preferred aspect, the present invention relates to theuse of two (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via a linker.

In a preferred aspect, the two amino acid sequences used in preparingthe bivalent polypeptide comprise or essentially consist of one of SEQID NO's: 60-76.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or a            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via a linker.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via a linker.

In a preferred aspect, the two amino acid sequences used in preparing abivalent polypeptide comprise or essentially consist of one of SEQ IDNO's: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via a linker.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via a linker.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequence, optionally via one or more linkers.

In a preferred aspect, the amino acid sequences used in preparing abivalent polypeptide comprises or essentially consists of one of SEQ IDNO's: 146-153.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Girt, Q) at position 105 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino add sequence to at least one further            amino acid sequence, optionally via one or more linkers.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequences used in preparing abivalent polypeptide comprises or essentially consists of one of SEQ IDNO's: 146-149 and 151-153.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight or nine, ten, eleven or twelve)amino acid residues have been mutated selected from the following:Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, in preparing abivalent polypeptide.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight or nine) amino acid residues havebeen mutated selected from the following: Val5Leu, Ala14Pro, Glu44Gly,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, inpreparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three or four) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, in preparing abivalent polypeptide.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six or seven) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,Asp85Glu, Arg105Gln and Gln108Leu, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use oftwo (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which following amino acidresidues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp; or    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,        in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the above wherein the amino acid(Glutamic acid) at position 1 has been changed into Aspartic acid, inpreparing a bivalent polypeptide.

In this respect, the present invention relates to the use of an aminoacid sequence chosen from the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a bivalent polypeptide. The method for the            preparation of the bivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing abivalent polypeptide comprises or essentially consists of SEQ ID NO:138. In another preferred aspect, the amino acid sequence used inpreparing a bivalent polypeptide comprises or essentially consists ofSEQ ID NO: 139. In another preferred aspect, the amino acid sequenceused in preparing a bivalent polypeptide comprises or essentiallyconsists of SEQ ID NO: 140. In another preferred aspect, the amino acidsequence used in preparing a bivalent polypeptide comprises oressentially consists of SEQ ID NO: 141. In another preferred aspect, theamino acid sequence used in preparing a bivalent polypeptide comprisesor essentially consists of SEQ ID NO: 154-157.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which Glutamic acid at position I has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 62, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 65, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 76, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 75, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 147, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 149, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 153, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine, ten, eleven or twelve) amino acid residues have beenmutated selected from the following: Val5Leu, Ala14Pro, Ser19R,Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, and wherein Glutamic add at position 1 has beenchanged into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,Gln, Gln108Leu and Gly54Asp, and wherein Glutamic acid at position 1 hasbeen changed into Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three or four) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu and Gln108Leu, and wherein Glutamic acid at position1 has been changed into Aspartic acid, in preparing a bivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six orseven) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Glnand Gln108Leu, and wherein Glutamic acid at position 1 has been changedinto Aspartic acid, in preparing a bivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which following amino acid residues have been mutated:

-   -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln,        in preparing a bivalent polypeptide.

The present invention also relates to the use of three amino acidsequences and/or Nanobodies® of the invention (as described above) inpreparing a trivalent polypeptide. The method for the preparation of thetrivalent polypeptide will comprise the linking of the amino acidsequences and/or Nanobodies® of the invention, optionally via one or twolinkers.

In a preferred aspect, the present invention relates to the use of three(preferably identical) amino acid sequences chosen from the following:

-   -   a) SEQ ID NO's: 50-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via one or two linkers.

In a preferred aspect, the three amino acid sequences used in preparingthe trivalent polypeptide comprise or essentially consist of one of SEQID NO's: 60-76.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or a            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via one or two linkers.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID N0's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequence to each other,            optionally via one or two linkers.

In a preferred aspect, the three amino acid sequences used in preparinga trivalent polypeptide comprise or essentially consist of one of SEQ IDNO's: 62, 65, 67, 68, 75 and 76.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequences to each other,            optionally via one or two linkers.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino add sequences to each other,            optionally via one or two linkers.

In a preferred aspect, the three amino acid sequences used in preparingthe trivalent polypeptide comprise or essentially consist of SEQ ID NO:65. In another preferred aspect, the three amino acid sequences used inpreparing the trivalent polypeptide comprise or essentially consist ofSEQ ID NO: 76.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequence, optionally via one or two linkers.

In a preferred aspect, the amino acid sequences used in preparing atrivalent polypeptide comprise or essentially consist of one of SEQ IDNO's: 146-153.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequence, optionally via one or two linkers.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences chosen from thefollowing:

-   -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and/or Leucine (Leu, L) at position            108 and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 so that when the amino acid            sequence has no more than 3, preferably no more than 2, more            preferably no more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequence to at least one further            amino acid sequence, optionally via one or two linkers.

In a preferred aspect, the amino acid sequences used in preparing atrivalent polypeptide comprises or essentially consists of one of SEQ IDNO's: 146-149 and 151-153.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight or nine, ten, eleven or twelve)amino acid residues have been mutated selected from the following:Val5Leu, Ala14Pro, Ser19Arg, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, in preparing atrivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six, seven, eight or nine) amino acid residues havebeen mutated selected from the following: Val5Leu, Ala14Pro, Glu44Gly,Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, inpreparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three or four) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, in preparing atrivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which one or more (such as two,three, four, five, six or seven) amino acid residues have been mutatedselected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,Asp85Glu, Arg105Gln and Gln108Leu, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofthree (preferably identical) amino acid sequences that comprises oressentially consists of SEQ ID NO: 5, in which following amino acidresidues have been mutated:

-   -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,        in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 62 in preparing SEQ ID NO: 77. The method for the preparationof the multivalent polypeptide will comprise the linking of an aminoacid sequence with SEQ ID NO: 62 to at least two further amino acidsequences with SEQ ID NO: 62, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 65 in preparing SEQ ID NO: 78. The method for the preparationof the multivalent polypeptide will comprise the linking of an aminoacid sequence with SEQ ID NO: 65 to at least two further amino acidsequences with SEQ ID NO: 65, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 76 in preparing SEQ ID NO: 79. The method for the preparationof the multivalent polypeptide will comprise the linking of an aminoacid sequence with SEQ ID NO: 76 to at least two further amino acidsequences with SEQ ID NO: 76, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 75 in preparing SEQ ID NO: 158. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 75 to at least two further aminoacid sequences with SEQ ID NO: 75, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 147 in preparing SEQ ID NO: 159. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 147 to at least two further aminoacid sequences with SEQ ID NO: 147, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 149 in preparing SEQ ID NO: 160. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 149 to at least two further aminoacid sequences with SEQ ID NO: 149, via a 1505 (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 153 in preparing SEQ ID NO: 161. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 153 to at least two further aminoacid sequences with SEQ ID NO: 153, via a 15GS (SEQ ID NO: 128) linker.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence chosen from the above wherein the amino acid(Glutamic acid) at position 1 has been changed into Aspartic acid, inpreparing a trivalent polypeptide.

In this respect, the present invention relates to the use of an aminoacid sequence chosen from the following:

-   -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,            in preparing a trivalent polypeptide. The method for the            preparation of the trivalent polypeptide will comprise the            linking of said amino acid sequence to at least two further            amino acid sequences, optionally via one or more linkers.

In a preferred aspect, the amino acid sequence used in preparing atrivalent polypeptide comprises or essentially consists of SEQ ID NO:138. In another preferred aspect, the amino acid sequence used inpreparing a trivalent polypeptide comprises or essentially consists ofSEQ ID NO: 139. In another preferred aspect, the amino acid sequenceused in preparing a trivalent polypeptide comprises or essentiallyconsists of SEQ ID NO: 140. In another preferred aspect, the amino acidsequence used in preparing a trivalent polypeptide comprises oressentially consists of SEQ ID NO: 141. In another preferred aspect, theamino acid sequence used in preparing a trivalent polypeptide comprisesor essentially consists of one of SEQ ID NO's: 154-157.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 62, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 65, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 76, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 75, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 147, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 149, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 153, in which Glutamic acid at position 1 has been changed intoAspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine, ten, eleven or twelve) amino acid residues have beenmutated selected from the following: Val5Leu, Ala14Pro, Ser19R,Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,Gln108Leu and Gly54Asp, and wherein Glutamic acid at position 1 has beenchanged into Aspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six, seven,eight or nine) amino acid residues have been mutated selected from thefollowing: Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,Arg105Gln, Gln108Leu and Gly54Asp, and wherein Glutamic acid at position1 has been changed into Aspartic acid, in preparing a trivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three or four) amino acidresidues have been mutated selected from the following: Ala14Pro,Ser19Arg, Ile20Leu and Gln108Leu, and wherein Glutamic acid at position1 has been changed into Aspartic acid, in preparing a trivalentpolypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which one or more (such as two, three, four, five, six orseven) amino acid residues have been mutated selected from thefollowing: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Glnand Gln108Leu, and wherein Glutamic acid at position 1 has been changedinto Aspartic acid, in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofan amino acid sequence that comprises or essentially consists of SEQ IDNO: 5, in which following amino acid residues have been mutated:

-   -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln,        in preparing a trivalent polypeptide.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 138 in preparing SEQ ID NO: 142. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 138 to at least two further aminoacid sequences (preferably SEQ ID NO: 5), via a 15GS (SEQ ID NO: 128)linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 139 in preparing SEQ ID NO: 143. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 139 to at least two further aminoacid sequences (preferably SEQ ID NO: 62), via a 15GS (SEQ ID NO: 128)linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 140 in preparing SEQ ID NO: 144. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 140 to at least two further aminoacid sequences (preferably SEQ ID NO: 65), via a 15GS (SEQ ID NO: 128)linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 154 in preparing SEQ ID NO: 162. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 154 to at least two further aminoacid sequences (preferably SEQ ID NO: 75), via a 15GS (SEQ ID NO: 128)linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 155 in preparing SEQ ID NO: 163. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 155 to at least two further aminoacid sequences (preferably SEQ ID NO: 147), via a 15GS (SEQ ID NO: 128)linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 156 in preparing SEQ ID NO: 164. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 156 to at least two further aminoacid sequences (preferably SEQ ID NO: 149), via a 15GS (SEQ ID NO: 128)linker.

In another preferred aspect, the present invention relates to the use ofSEQ ID NO: 157 in preparing SEQ ID NO: 165. The method for thepreparation of the multivalent polypeptide will comprise the linking ofan amino acid sequence with SEQ ID NO: 157 to at least two further aminoacid sequences (preferably SEQ ID NO: 153), via a 15GS (SEQ ID NO: 128)linker.

Polypeptides of the invention that contain at least two amino acidsequences and/or Nanobodies®, in which at least one amino acid sequenceor Nanobody® is directed against a first antigen (i.e. against protein Fof hRSV) and at least one amino acid sequence or Nanobody® is directedagainst a second antigen (i.e. different from protein F of hRSV), willalso be referred to as “multispecific” polypeptides of the invention,and the amino acid sequences or Nanobodies® present in such polypeptideswill also be referred to herein as being in a “multispecific format”.Thus, for example, a “bispecific” polypeptide of the invention is apolypeptide that comprises at least one amino acid sequence or Nanobody®of the invention directed against a first antigen (i.e. protein F ofhRSV) and at least one further amino acid sequence or Nanobody® directedagainst a second antigen (i.e. different from protein F of hRSV),whereas a “trispecific” polypeptide of the invention is a polypeptidethat comprises at least one amino acid sequence or Nanobody® of theinvention directed against a first antigen (i.e. protein F of hRSV), atleast one further amino acid sequence or Nanobody® directed against asecond antigen (i.e. different from protein F of hRSV) and at least onefurther amino acid sequence or Nanobody® directed against a thirdantigen (i.e. different from both protein F of hRSV and the secondantigen); etc.

Accordingly, in its simplest form, a bispecific polypeptide of theinvention is a bivalent polypeptide of the invention (as definedherein), comprising a first amino acid sequence or Nanobody® of theinvention directed against protein F of hRSV, and a second amino acidsequence or Nanobody® directed against a second antigen, in which saidfirst and second amino acid sequence or Nanobody® may optionally belinked via a linker sequence (as defined herein); whereas a trispecificpolypeptide of the invention in its simplest form is a trivalentpolypeptide of the invention (as defined herein), comprising a firstamino acid sequence or Nanobody® of the invention directed againstprotein F of hRSV, a second amino acid sequence or Nanobody® directedagainst a second antigen and a third amino acid sequence or Nanobody®directed against a third antigen, in which said first, second and thirdamino acid sequence or Nanobody® may optionally be linked via one ormore, and in particular two, linker sequences.

In a specific aspect, the polypeptide of the invention is a trivalent,bispecific polypeptide. A trivalent, bispecific polypeptide of theinvention in its simplest form may be a trivalent polypeptide of theinvention (as defined herein), comprising two identical amino acidsequences or Nanobodies® against protein F of hRSV and a third aminoacid sequence or Nanobody® directed against another antigen, in whichsaid first, second and third amino acid sequence or Nanobody® mayoptionally be linked via one or more, and in particular two, linkersequences.

A preferred, but non-limiting example of a multispecific polypeptide ofthe invention comprises at least one amino acid sequence or Nanobody® ofthe invention and at least one Nanobody® that provides for an increasedhalf-life. Some preferred, but non-limiting examples of such Nanobodies®include Nanobodies® directed against serum proteins, such as human serumalbumin, thyroxine-binding protein, (human) transferrin, fibrinogen, animmunoglobulin such as IgG, IgE or igM, or one of the other serumproteins listed in WO 04/003019.

For example, for experiments in mice, Nanobodies® against mouse serumalbumin (MSA) can be used, whereas for pharmaceutical use, Nanobodies®against human serum albumin can be used.

Another embodiment of the present invention is a polypeptide constructas described above wherein said at least one (human) serum protein isany of (human) serum albumin, (human) serum immunoglobulins, (human)thyroxine-binding protein, (human) transferrin, (human) fibrinogen, etc.

Accordingly, in a specific aspect, the polypeptide of the invention is abispecific polypeptide comprising a first amino acid sequence orNanobody® of the invention against protein F of hRSV and a second aminoacid sequence or Nanobody® directed against (human) serum albumin, inwhich said first and second amino acid sequence or Nanobody® mayoptionally be linked via a linker sequence.

In another specific aspect, the polypeptide of the invention is atrivalent, bispecific polypeptide, comprising two identical amino acidsequences or Nanobodies® of the invention against protein F of hRSV anda third amino acid sequence or Nanobody® directed against (human) serumalbumin, in which said first, second and third amino acid sequence orNanobody® may optionally be linked via one or more, and in particulartwo, linker sequences.

In another specific aspect, the polypeptide of the invention is atetravalent, bispecific polypeptide, comprising three identical aminoacid sequences or Nanobodies® of the invention against protein F of hRSVand a fourth amino acid sequence or Nanobody® directed against (human)serum albumin, in which said first, second, third and fourth amino acidsequence or Nanobody® may optionally be linked via one or more, and inparticular two or three, linker sequences.

According to a specific, but non-limiting aspect of the invention, thepolypeptides of the invention contain, besides the one or more aminoacid sequences or Nanobodies® of the invention, at least one Nanobody®against human serum albumin. These Nanobodies® against human serumalbumin may be as generally described in the applications by Ablynx N.V. cited above (see for example WO 04/062551). Some particularlypreferred Nanobodies® that provide for increased half-life and that canbe used in the polypeptides of the invention include the Nanobodies®ALB-1 to ALB-10 disclosed in WO 06/122787 (see Tables II and III) ofwhich ALB-8 (SEQ ID NO: 62 in WO 06/122787) is particularly preferred.

In another aspect, the invention relates to a compound or construct, andin particular a protein or polypeptide (also referred to herein as a“compound of the invention”) that comprises or essentially consists ofone or more amino acid sequences, Nanobodies® and/or polypeptides of theinvention (or suitable fragments thereof), and optionally furthercomprises one or more other groups, residues, moieties or binding units.As will become clear to the skilled person from the further disclosureherein, such further groups, residues, moieties, binding units or aminoacid sequences may or may not provide further functionality to the aminoacid sequence, Nanobody® or polypeptide of the invention (and/or to thecompound. construct or polypeptide in which it is present) and may ormay not modify the properties of the amino acid sequence, Nanobody®and/or polypeptide of the invention.

Such groups, residues, moieties or binding units may for example bechemical groups, residues, moieties, which may or may not by themselvesbe biologically and/or pharmacologically active. For example, andwithout limitation, such groups may be linked to the one or more aminoacid sequences, Nanobodies® and/or polypeptides of the invention so asto provide a “derivative” of an amino acid sequence, Nanobody® and/orpolypeptide of the invention, as further described herein.

Also within the scope of the present invention are compounds orconstructs that comprise or essentially consist of one or more derivatesas described herein, and optionally further comprise one or more othergroups, residues, moieties or binding units, optionally linked via oneor more linkers. Preferably, said one or more other groups, residues,moieties or binding units are amino acid sequences.

In the compounds, constructs or polypeptides described above, the one ormore amino acid sequences, Nanobodies® and/or polypeptides of theinvention and the one or more groups, residues, moieties or bindingunits may be linked directly to each other and/or via one or moresuitable linkers or spacers. For example, when the one or more groups,residues, moieties or binding units are amino acid sequences, thelinkers may also be amino acid sequences, so that the resultingcompound, construct or polypeptide is a fusion (protein) or fusion(polypeptide).

A compound or construct of the invention may comprises an amino acidsequence, Nanobody® or polypeptide of the invention, which is fused atits amino terminal end, at its carboxy terminal end, or both at itsamino terminal end and at its carboxy terminal end to at least onefurther amino acid sequence, i.e. so as to provide a fusion proteincomprising said amino acid sequence, Nanobody® or polypeptide of theinvention and the one or more further amino acid sequences.

The one or more further amino acid sequence may be any suitable and/ordesired amino acid sequences. The further amino acid sequences may ormay not change, alter or otherwise influence the (biological) propertiesof the amino acid sequence, Nanobody® or polypeptide of the invention,and may or may not add further functionality to the amino acid sequence,Nanobody® or the polypeptide of the invention. Preferably, the furtheramino acid sequence is such that it confers one or more desiredproperties or functionalities to the amino acid sequence, Nanobody® orthe polypeptide of the invention.

Example of such amino acid sequences will be clear to the skilledperson, and may generally comprise all amino acid sequences that areused in peptide fusions based on conventional antibodies and fragmentsthereof (including but not limited to ScFv's and single domainantibodies). Reference is for example made to the review by Holliger andHudson, Nature Biotechnology, 23, 9, 1126-1136 (2005).

For example, such an amino acid sequence may be an amino acid sequencethat increases the half-life, the solubility, or the absorption, reducesthe immunogenicity or the toxicity, eliminates or attenuates undesirableside effects, and/or confers other advantageous properties to and/orreduces the undesired properties of the compounds of the invention,compared to the amino acid sequence, Nanobody® or polypeptide of theinvention per se. Some non-limiting examples of such amino acidsequences are serum proteins, such as human serum albumin (see forexample WO 00/27435) or haptenic molecules (for example haptens that arerecognized by circulating antibodies, see for example WO 98/22141).

The further amino acid sequence may also provide a second binding site,which binding site may be directed against any desired protein,polypeptide, antigen, antigenic determinant or epitope (including butnot limited to the same protein, polypeptide, antigen, antigenicdeterminant or epitope against which the amino acid sequence orNanobody® of the invention is directed, or a different protein,polypeptide, antigen, antigenic determinant or epitope). For example,the further amino acid sequence may provide a second binding site thatis directed against a serum protein (such as, for example, human serumalbumin or another serum protein such as IgG), so as to provideincreased half-life in serum. Such amino acid sequences for exampleinclude Nanobodies®, as well as the small peptides and binding proteinsdescribed in WO 91/01743, WO 01/45746 and WO 02/076489 and the dAb'sdescribed in WO 03/002609 and WO 04/003019. Reference is also made toHarmsen et al., Vaccine, 23 (41); 4926-42, 2005, as well as to EP 0 368684, as well as to WO 08/028,977, WO 08/043,821, WO 08/043,822 by AblynxN. V. and WO 08/068,280.

Such amino acid sequences may in particular be directed against serumalbumin (and more in particular human serum albumin) and/or against IgG(and more in particular human IgG). For example, such amino acidsequences may be amino acid sequences that are directed against (human)serum albumin and amino acid sequences that can bind to amino acidresidues on (human) serum albumin that are not involved in binding ofserum albumin to FcRn (see for example WO 06/0122787) and/or amino acidsequences that are capable of binding to amino acid residues on serumalbumin that do not form part of domain III of serum albumin (see againfor example WO 06/0122787); amino acid sequences that have or canprovide an increased half-life (see for example WO 08/028,977); aminoacid sequences against human serum albumin that are cross-reactive withserum albumin from at least one species of mammal, and in particularwith at least one species of primate (such as, without limitation,monkeys from the genus Macaca (such as, and in particular, cynomolgusmonkeys (Macaca fascicularis) and/or rhesus monkeys (Macaca mulatta))and baboon (Papio ursinus), reference is again made to WO 08/028,977);amino acid sequences that can bind to serum albumin in a pH independentmanner (see for example WO 08/043,821) and/or amino acid sequences thatare conditional binders (see for example WO 08/043,822).

According to another embodiment, the one or more further amino acidsequences may comprise one or more parts, fragments or domains ofconventional 4-chain antibodies (and in particular human antibodies)and/or of heavy chain antibodies. For example, although usually lesspreferred, an amino acid sequence, Nanobody® or polypeptide of theinvention may be linked to a conventional (preferably human) V_(H) orV_(L) domain or to a natural or synthetic analog of a V_(H) or V_(L)domain, again optionally via a linker sequence (including but notlimited to other (single) domain antibodies, such as the dAb's describedby Ward et al.).

Accordingly, in the compound or construct of the invention, said one ormore other groups, residues, moieties or binding units may be chosenfrom the group consisting of domain antibodies, amino acid sequencesthat are suitable for use as a domain antibody, single domainantibodies, amino acid sequences that are suitable for use as a singledomain antibody, “dAb's”, amino acid sequences that are suitable for useas a dAb, or Nanobodies®.

In one specific aspect of the invention, the compound, construct orpolypeptide of the invention comprising at least one amino acidsequence, Nanobody® or polypeptide of the invention may have anincreased half-life, compared to the corresponding amino acid sequence,Nanobody® or polypeptide of the invention. Some preferred, butnon-limiting examples of such compounds, constructs and polypeptideswill become clear to the skilled person based on the further disclosureherein, and for example comprise amino acid sequences, Nanobodies® orpolypeptides of the invention that have been chemically modified toincrease the half-life thereof (for example, by means of pegylation); orcompounds of the invention that comprise at least one amino acidsequence, Nanobody® or polypeptide of the invention that is linked to atleast one moiety (and in particular at least one amino acid sequence)that increases the half-life of the amino acid sequence, Nanobody® orpolypeptide of the invention. Examples of compounds of the inventionthat comprise such half-life extending moieties will become clear to theskilled person based on the further disclosure herein; and for exampleinclude, without limitation, compounds in which the one or more aminoacid sequences, Nanobodies® or polypeptides of the invention aresuitable linked to one or more serum proteins or fragments thereof (suchas serum albumin or suitable fragments thereof) or to one or morebinding units that can bind to serum proteins (such as, for example,Nanobodies® or (single) domain antibodies that can bind to serumproteins such as serum albumin, serum immunoglobulins such as IgG, ortransferrine); compounds in which an amino acid sequence, Nanobody® orpolypeptide of the invention is linked to an Fc portion (such as a humanFc) or a suitable part or fragment thereof; or compounds in which theone or more amino acid sequences, Nanobodies® or polypeptides of theinvention are suitable linked to one or more small proteins or peptidesthat can bind to serum proteins (such as, without limitation, theproteins and peptides described in WO 91/01743, WO 01/45746, WO02/076489).

The at least one amino acid sequence, Nanobody® or polypeptide may alsobe linked to one or more (preferably human) C_(H)1, C_(H)2 and/or C_(H)3domains, optionally via a linker sequence. For instance, an amino acidsequence, Nanobody® or polypeptide linked to a suitable C_(H)1 domaincould for example be used—together with suitable light chains—togenerate antibody fragments/structures analogous to conventional Fabfragments or F(ab′)₂ fragments, but in which one or (in case of anF(ab′)₂ fragment) one or both of the conventional V_(H) domains havebeen replaced by an amino acid sequence, Nanobody® or polypeptide of theinvention. Also, two amino acid sequences or Nanobodies® could be linkedto a C_(H)3 domain (optionally via a linker) to provide a construct withincreased half-life in vivo.

According to one specific aspect, one or more amino acid sequences,Nanobodies® or polypeptides of the invention may be linked (optionallyvia a suitable linker or hinge region) to one or more constant domains(for example, 2 or 3 constant domains that can be used as part of/toform an Fc portion), to an Fc portion and/or to one or more antibodyparts, fragments or domains that confer one or more effector functionsto the amino acid sequence, Nanobody® or polypeptide of the inventionand/or may confer the ability to bind to one or more Fc receptors. Forexample, for this purpose, and without being limited thereto, the one ormore further amino acid sequences may comprise one or more C_(H)2 and/orC_(H)3 domains of an antibody, such as from a heavy chain antibody (asdescribed herein) and more preferably from a conventional human 4-chainantibody; and/or may form (part of) and Fc region, for example from IgG(e.g. from IgG1, IgG2, IgG3 or IgG4), from IgE or from another human Igsuch as IgA, IgD or IgM. For example, WO 94/04678 describes heavy chainantibodies comprising a Camelid V_(HH) domain or a humanized derivativethereof (i.e. a Nanobody®), in which the Camelidae C_(H)2 and/or C_(H)5domain have been replaced by human C_(H)2 and C_(H)3 domains, so as toprovide an immunoglobulin that consists of 2 heavy chains eachcomprising a Nanobody® and human C_(H)2 and C_(H)3 domains (but noC_(H)1 domain), which immunoglobulin has the effector function providedby the C_(H)2 and C_(H)3 domains and which immunoglobulin can functionwithout the presence of any light chains. Other amino acid sequencesthat can be suitably linked to the amino acid sequences, Nanobodies® orpolypeptides of the invention so as to provide an effector function willbe clear to the skilled person, and may be chosen on the basis of thedesired effector function(s). Reference is for example made to WO04/058820, WO 99/42077, WO 02/056910 and WO 05/017148, as well as thereview by Holliger and Hudson, supra; and to WO 09/068,628. Coupling ofan amino acid sequence, Nanobody® or polypeptide of the invention to anFc portion may also lead to an increased half-life, compared to thecorresponding amino acid sequence, Nanobody® or polypeptide of theinvention. For some applications, the use of an Fc portion and/or ofconstant domains (i.e. C_(H)2 and/or C_(H)3 domains) that conferincreased half-life without any biologically significant effectorfunction may also be suitable or even preferred. Other suitableconstructs comprising one or more amino acid sequences, Nanobodies® orpolypeptides and one or more constant domains with increased half-lifein vivo will be clear to the skilled person, and may for examplecomprise amino acid sequences, Nanobodies® or polypeptides linked to aC_(H)3 domain, optionally via a linker sequence. Generally, any fusionprotein or derivatives with increased half-life will preferably have amolecular weight of more than 50 kD, the cut-off value for renalabsorption.

In another specific, but non-limiting, aspect, in order to form acompound of the invention, one or more amino acid sequences, Nanobodies®or polypeptides of the invention may be linked (optionally via asuitable linker or hinge region) to naturally occurring, synthetic orsemisynthetic constant domains (or analogs, variants, mutants, parts orfragments thereof) that have a reduced (or essentially no) tendency toself-associate into dimers (i.e. compared to constant domains thatnaturally occur in conventional 4-chain antibodies). Such monomeric(i.e. not self-associating) Fc chain variants, or fragments thereof,will be clear to the skilled person. For example, Helm et al., J BiolChem 1996 271 7494, describe monomeric Fc chain variants that can beused in the polypeptide chains of the invention.

Also, such monomeric Fc chain variants are preferably such that they arestill capable of binding to the complement or the relevant Fcreceptor(s) (depending on the Fc portion from which they are derived),and/or such that they still have some or all of the effector functionsof the Fc portion from which they are derived (or at a reduced levelstill suitable for the intended use). Alternatively, in such apolypeptide chain of the invention, the monomeric Fc chain may be usedto confer increased half-life upon the polypeptide chain, in which casethe monomeric Fc chain may also have no or essentially no effectorfunctions.

Generally, the amino acid sequences, Nanobodies® or polypeptides of theinvention (or compounds, constructs or comprising the same) withincreased half-life preferably have a half-life that is at least 1.5times, preferably at least 2 times, such as at least 5 times, forexample at least 10 times or more than 20 times, greater than thehalf-life of the corresponding amino acid sequence, Nanobody® orpolypeptide of the invention per se. For example, the amino acidsequences, Nanobodies®, compounds, constructs or polypeptides of theinvention with increased half-life may have a half-life that isincreased with more than 1 hours, preferably more than 2 hours, morepreferably more than 6 hours, such as more than 12 hours, or even morethan 24, 48 or 72 hours, compared to the corresponding amino acidsequence, Nanobody® or polypeptide of the invention per se.

In a preferred, but non-limiting aspect of the invention, such aminoacid sequences, Nanobodies®, compound, constructs or polypeptides of theinvention exhibit a serum half-life in human of at least about 12 hours,preferably at least 24 hours, more preferably at least 48 hours, evenmore preferably at least 72 hours or more. For example, compounds orpolypeptides of the invention may have a half-life of at least 5 days(such as about 5 to 10 days), at preferably at least 9 days (such asabout 9 to 14 days), more preferably at least about 10 days (such asabout 10 to 15 days), or at least about 11 days (such as about 11 to 16days), more preferably at least about 12 days (such as about 12 to 18days or more), or more than 14 days (such as about 14 to 19 days).

The further amino acid sequences may also form a signal sequence orleader sequence that directs secretion of the amino acid sequence,Nanobody® or the polypeptide of the invention from a host cell uponsynthesis (for example to provide a pre-, pro- or prepro-form of thepolypeptide of the invention, depending on the host cell used to expressthe polypeptide of the invention).

The further amino acid sequence may also form a sequence or signal thatallows the amino acid sequence, Nanobody® or polypeptide of theinvention to be directed towards and/or to penetrate or enter intospecific organs, tissues, cells, or parts or compartments of cells,and/or that allows the amino acid sequence, Nanobody® or polypeptide ofthe invention to penetrate or cross a biological barrier such as a cellmembrane, a cell layer such as a layer of epithelial cells. Suitableexamples of such amino acid sequences will be clear to the skilledperson, and for example include, but are not limited to, the “Peptrans”vectors mentioned above, the sequences described by Cardinale et al. andthe amino acid sequences and antibody fragments known per se that can beused to express or produce the Nanobodies® and polypeptides of theinvention as so-called “intrabodies”, for example as described in WO94/02610, WO 95/22618, U.S. Pat. No. 7,004,940, WO 03/014960, WO99/07414; WO 05/01690; EP 1 512 696; and in Cattaneo, A. & Biocca, S.(1997) intracellular Antibodies: Development and Applications. Landesand Springer-Verlag; and in Kontermann, Methods 34, (2004), 163-170, andthe further references described therein.

Such a protein, polypeptide, compound or construct may also be inessentially isolated form (as defined herein).

The compounds or polypeptides of the invention can generally be preparedby a method which comprises at least the step of suitably linking theone or more amino acid sequences, Nanobodies®, monovalent constructsand/or polypeptides of the invention to the one or more further groups,residues, moieties or binding units, optionally via the one or moresuitable linkers, so as to provide the compound or polypeptide of theinvention. Polypeptides of the invention can also be prepared by amethod which generally comprises at least the steps of providing anucleic acid that encodes a polypeptide of the invention, expressingsaid nucleic acid in a suitable manner, and recovering the expressedpolypeptide of the invention. Such methods can be performed in a mannerknown per se, which will be clear to the skilled person, for example onthe basis of the methods and techniques further described herein.

Suitable spacers or linkers for use in multivalent and/or multispecificpolypeptides or constructs will be clear to the skilled person, and maygenerally be any linker or spacer used in the art to link amino acidsequences. Preferably, said linker or spacer is suitable for use inconstructing proteins or polypeptides that are intended forpharmaceutical use.

Some particularly preferred spacers include the spacers and linkers thatare used in the art to link antibody fragments or antibody domains.These include the linkers mentioned in the general background art citedabove, as well as for example linkers that are used in the art toconstruct diabodies or ScFv fragments (in this respect, however, itsshould be noted that, whereas in diabodies and in ScFv fragments, thelinker sequence used should have a length, a degree of flexibility andother properties that allow the pertinent V_(H) and V_(L) domains tocome together to form the complete antigen-binding site, there is noparticular limitation on the length or the flexibility of the linkerused in the polypeptide of the invention, since each amino acid sequenceor Nanobody® by itself forms a complete antigen-binding site).

For example, a linker may be a suitable amino acid sequence, and inparticular amino acid sequences of between 1 and 50, preferably between1 and 30, such as between 1 and 10 amino acid residues. Some preferredexamples of such amino acid sequences include gly-ser linkers, forexample of the type (gly_(x)ser_(y))_(z), such as (for example (gly₄ser)₃ or (gly₃ser₂)₃, as described in WO 99/42077, hinge-like regionssuch as the hinge regions of naturally occurring heavy chain antibodiesor similar sequences (such as described in WO 94/04678).

Some other particularly preferred linkers are poly-alanine (such asAAA), as well as the linkers mentioned in Table A-7, of which GS15 isparticularly preferred.

Other suitable linkers generally comprise organic compounds or polymers,in particular those suitable for use in proteins for pharmaceutical use.For instance, poly(ethyleneglycol) moieties have been used to linkantibody domains, see for example WO 04/081026.

It is encompassed within the scope of the invention that the length, thedegree of flexibility and/or other properties of the linker(s) used(although not critical, as it usually is for linkers used in ScFvfragments) may have some influence on the properties of the finalpolypeptide of the invention, including but not limited to the affinity,specificity or avidity for protein F of hRSV, or for one or more of theother antigens. Based on the disclosure herein, the skilled person willbe able to determine the optimal linker(s) for use in a specificpolypeptide of the invention, optionally after some limited routineexperiments.

It is also within the scope of the invention that the linker(s) usedconfer one or more other favourable properties or functionality to thepolypeptides of the invention, and/or provide one or more sites for theformation of derivatives and/or for the attachment of functional groups(e.g. as described herein for the derivatives of the amino acidsequences, Nanobodies®, compounds and polypeptides of the invention).For example, linkers containing one or more charged amino acid residuescan provide improved hydrophilic properties, whereas linkers that formor contain small epitopes or tags can be used for the purposes ofdetection, identification and/or purification. Again, based on thedisclosure herein, the skilled person will be able to determine theoptimal linkers for use in a specific polypeptide of the invention,optionally after some limited routine experiments.

Finally, when two or more linkers are used in the polypeptides of theinvention, these linkers may be the same or different. Again, based onthe disclosure herein, the skilled person will be able to determine theoptimal linkers for use in a specific polypeptide of the invention,optionally after some limited routine experiments.

Usually, for ease of expression and production, a polypeptide of theinvention will be a linear polypeptide. However, the invention in itsbroadest sense is not limited thereto. For example, when a polypeptideof the invention comprises three of more amino acid sequences orNanobodies®, it is possible to link them by use of a linker with threeor more “arms”, which each “arm” being linked to an amino acid sequenceor Nanobody®, so as to provide a “star-shaped” construct. It is alsopossible, although usually less preferred, to use circular constructs.

As will also be clear from the disclosure herein, it is also within thescope of the invention to use parts or fragments, or combinations of twoor more parts or fragments, of the amino acid sequences, Nanobodies® orpolypeptides of the invention as defined herein, and in particular partsor fragments of the amino acid sequences of SEQ ID NO's: 50-76, 138-141and 146-157 or the polypeptides of SEQ ID N0's: 77-79, 142-145 and158-165. Thus, according to one embodiment of the invention, the term“amino acid sequence of the invention”, “Nanobody® of the invention” and“polypeptide of the invention” in its broadest sense also covers suchparts or fragments.

Generally, such parts or fragments of the amino acid sequences,Nanobodies® or polypeptides of the invention (including variants thereofas defined herein) have amino acid sequences in which, compared to theamino acid sequence of the corresponding full length amino acid sequenceor Nanobody® of the invention, one or more of the amino acid residues atthe N-terminal end, one or more amino acid residues at the &terminalend, one or more contiguous internal amino acid residues, or anycombination thereof, have been deleted and/or removed.

The parts or fragments are preferably such that they can bind toantigenic site II on protein F of hRSV, with an affinity (suitablymeasured and/or expressed as a K_(D)-value (actual or apparent), aK_(A)-value (actual or apparent), a k_(on)-rate and/or a k_(off)-rate,or alternatively as an IC₅₀ value, as further described herein) that isas defined herein.

In particular, amino acid sequences, Nanobodies®, polypeptides and partsor fragments are preferably such that they:

-   -   bind to protein F of hRSV with a dissociation constant (K_(D))        of 1000 nM to 1 nM or less, preferably 100 nM to 1 nM or less,        more preferably 10 nM to 1 nM or less;        and/or such that they:    -   bind to protein F of hRSV with a k_(on)-rate of between 10⁴ M⁻¹        s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹ s⁻¹ and 10⁷        M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more;        and/or such that they:

bind to protein F of hRSV with a k_(off) rate between 10⁻² s⁻¹(t_(1/2)=0.50 s) and 10⁻⁴ s⁻¹ (providing a near irreversible complexwith a t_(1/2) of multiple days), preferably between 10⁻³ s⁻¹ and 10⁻⁴s⁻¹, or lower.

The affinity of the parts or fragments against protein F of hRSV, can bedetermined in a manner known per se, for example using the assaydescribed herein.

Such parts or fragments will usually also have a hRSV neutralizationefficacy and/or potency as defined herein.

Any part or fragment is preferably such that it comprises at least 10contiguous amino acid residues, preferably at least 20 contiguous aminoacid residues, more preferably at least 30 contiguous amino acidresidues, such as at least 40 contiguous amino acid residues, of theamino acid sequence of the corresponding full length amino acidsequence, Nanobody® or polypeptide of the invention.

Also, any part or fragment is such preferably that it comprises at leastone of the CDR's (and preferably at least CDR3 or part thereof) and atleast one other CDR (i.e. CDR1 or CDR2) or at least part thereof,preferably connected by suitable framework sequence(s) or at least partthereof. More preferably, any part or fragment is such that it comprisesat least one of the CDR's (and preferably at least CDR3 or part thereof)and at least part of the two remaining CDR's, again preferably connectedby suitable framework sequence(s) or at least part thereof.

According to another particularly preferred, but non-limitingembodiment, such a part or fragment comprises at least CDR3, such asFR3, CDR3 and FR4 of the corresponding full length Nanobody® of theinvention, i.e. as for example described in the Internationalapplication WO 03/050531 (tasters et al.).

As already mentioned above, it is also possible to combine two or moreof such parts or fragments (i.e. from the same or different amino acidsequences or Nanobodies® of the invention), i.e. to provide furtherparts or fragments (as defined herein) of an amino acid sequence, aNanobody® or a polypeptide of the invention. It is for example alsopossible to combine one or more parts or fragments of an amino acidsequence, a Nanobody® or a polypeptide of the invention with one or moreparts or fragments of a human V_(H) domain.

According to one preferred embodiment, the parts or fragments have adegree of sequence identity of at least 50%, preferably at least 60%,more preferably at least 70%, even more preferably at least 80%, such asat least 90%, 95% or 99% or more with one of the amino acid sequences orNanobodies® of SEQ ID NO's: 60-76, 138-141 and 146-157 or with one ofthe polypeptides of SEQ ID NO's: 77-79, 142-145 and 158-165.

The parts and fragments, and nucleic acid sequences encoding the same,can be provided and optionally combined in any manner known per se. Forexample, such parts or fragments can be obtained by inserting a stopcodon in a nucleic acid that encodes a full-sized amino acid sequence,Nanobody® or polypeptide of the invention, and then expressing thenucleic acid thus obtained in a manner known per se (e.g. as describedherein). Alternatively, nucleic acids encoding such parts or fragmentscan be obtained by suitably restricting a nucleic acid that encodes afull-sized amino acid sequence, Nanobody® or polypeptide of theinvention or by synthesizing such a nucleic acid in a manner known perse. Parts or fragments may also be provided using techniques for peptidesynthesis known per se.

The invention in its broadest sense also comprises derivatives of theamino acid sequences, Nanobodies®, compounds or polypeptides of theinvention. Such derivatives can generally be obtained by modification,and in particular by chemical and/or biological (e.g. enzymatical)modification, of the amino acid sequences, Nanobodies®, compounds orpolypeptides of the invention and/or of one or more of the amino acidresidues that form the amino acid sequences, Nanobodies®, compounds orpolypeptides of the invention.

Examples of such modifications, as well as examples of amino acidresidues within the amino acid sequence, Nanobody® sequence, compound orpolypeptide sequences that can be modified in such a manner (i.e. eitheron the protein backbone but preferably on a side chain), methods andtechniques that can be used to introduce such modifications and thepotential uses and advantages of such modifications will be clear to theskilled person.

For example, such a modification may involve the introduction (e.g. bycovalent linking or in an other suitable manner) of one or morefunctional groups, residues or moieties into or onto the amino acidsequence, Nanobody®, compound or polypeptide of the invention, and inparticular of one or more functional groups, residues or moieties thatconfer one or more desired properties or functionalities to the aminoacid sequence, Nanobody®, compound or polypeptide of the invention.Example of such functional groups will be clear to the skilled person.

For example, such modification may comprise the introduction (e.g. bycovalent binding or in any other suitable manner) of one or morefunctional groups that that increase the half-life, the solubilityand/or the absorption of the amino acid sequence, Nanobody®, compound orpolypeptide of the invention, that reduce the immunogenicity and/or thetoxicity of the amino acid sequence, Nanobody®, compound or polypeptideof the invention, that eliminate or attenuate any undesirable sideeffects of the amino acid sequence, Nanobody®, compound or polypeptideof the invention, and/or that confer other advantageous properties toand/or reduce the undesired properties of the amino acid sequence,Nanobody®, compound or polypeptide of the invention; or any combinationof two or more of the foregoing. Examples of such functional groups andof techniques for introducing them will be clear to the skilled person,and can generally comprise all functional groups and techniquesmentioned in the general background art cited hereinabove as well as thefunctional groups and techniques known per se for the modification ofpharmaceutical proteins, and in particular for the modification ofantibodies or antibody fragments (including ScFv's and single domainantibodies), for which reference is for example made to Remington'sPharmaceutical Sciences, 16th ed., Mack Publishing Co., Easton, Pa.(1980). Such functional groups may for example be linked directly (forexample covalently) to an amino acid sequence, Nanobody®, compound orpolypeptide of the invention, or optionally via a suitable linker orspacer, as will again be clear to the skilled person.

One of the most widely used techniques for increasing the half-lifeand/or reducing the immunogenicity of pharmaceutical proteins comprisesattachment of a suitable pharmacologically acceptable polymer, such aspoly(ethyleneglycol) (PEG) or derivatives thereof (such asmethoxypoly(ethyleneglycol) or mPEG). Generally, any suitable form ofpegylation can be used, such as the pegylation used in the art forantibodies and antibody fragments (including but not limited to (single)domain antibodies and ScFv's); reference is made to for example Chapman,Nat. Biotechnol., 54, 531-545 (2002); by Veronese and Harris, Adv. DrugDeliv. Rev. 54, 453-456 (2003), by Harris and Chess, Nat. Rev. Drug.Discov., 2, (2003) and in WO 04/060965. Various reagents for pegylationof proteins are also commercially available, for example from NektarTherapeutics, USA.

Preferably, site-directed pegylation is used, in particular via acysteine-residue (see for example Yang et al., Protein Engineering, 16,10, 761-770 (2003). For example, for this purpose, PEG may be attachedto a cysteine residue that naturally occurs in an amino acid sequence,Nanobody®, compound or polypeptide of the invention, an amino acidsequence, Nanobody®, compound or polypeptide of the invention may bemodified so as to suitably introduce one or more cysteine residues forattachment of PEG, or an amino acid sequence comprising one or morecysteine residues for attachment of PEG may be fused to the N- and/orC-terminus of an amino acid sequence, Nanobody®, compound or polypeptideof the invention, all using techniques of protein engineering known perse to the skilled person.

Preferably, for the amino acid sequences, Nanobodies®, compounds orpolypeptides of the invention of the invention, a PEG is used with amolecular weight of more than 5000, such as more than 10,000 and lessthan 200,000, such as less than 100,000; for example in the range of20,000-80,000.

Another, usually less preferred modification comprises N-linked orO-linked glycosylation, usually as part of co-translational and/orpost-translational modification, depending on the host cell used forexpressing the amino acid sequence, Nanobody®, compound or polypeptideof the invention.

Yet another modification may comprise the introduction of one or moredetectable labels or other signal-generating groups or moieties,depending on the intended use of the labelled amino acid sequence,Nanobody®, compound or polypeptide of the invention. Suitable labels andtechniques for attaching, using and detecting them will be clear to theskilled person, and for example include, but are not limited to,fluorescent labels (such as fluorescein, isothiocyanate, rhodamine,phycoerythrin, phycocyanin, allophycocyanin, o-phthaldehyde, andfluorescamine and fluorescent metals such as ¹⁵²Eu or others metals fromthe lanthanide series), phosphorescent labels, chemiluminescent labelsor bioluminescent labels (such as luminal, isoluminol, theromaticacridinium ester, imidazole, acridinium salts, oxalate ester, dioxetaneor CFP and its analogs), radio-isotopes (such as ³H, ¹²⁵I, ³²P, ³⁵S,¹⁴C, ⁵¹Cr, ³⁶Cl, ⁵⁷Co, ⁵⁸Co, ⁵⁹Fe, and ⁷⁵Se), metals, metals chelates ormetallic cations (for example metallic cations such as ^(99m)Tc, ¹²³I,¹¹¹In, ¹³¹I, ⁹⁷Ru, ⁶⁷Cu, ⁶⁷Ga, and ⁶⁸Ga or other metals or metalliccations that are particularly suited for use in in vivo, in vitro or insitu diagnosis and imaging, such as (¹⁵⁷Gd, ⁵⁵Mn, ¹⁶²Dy, ⁵²Cr, and⁵⁶Fe), as well as chromophores and enzymes (such as malatedehydrogenase, staphylococcal nuclease, delta-V-steroid isomerase, yeastalcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triosephosphate isomerase, biotinavidin peroxidase, horseradish peroxidase,alkaline phosphatase, asparaginase, glucose oxidase, β-galactosidase,ribonuclease, urease, catalase, glucose-VI-phosphate dehydrogenase,glucoamylase and acetylcholine esterase). Other suitable labels will beclear to the skilled person, and for example include moieties that canbe detected using NMR or ESR spectroscopy.

Such labelled amino acid sequences, Nanobodies®, compounds orpolypeptides of the invention may for example be used for in vitro, invivo or in situ assays (including immunoassays known per se such asELISA, RIA, EIA and other “sandwich assays”, etc.) as well as in vivodiagnostic and imaging purposes, depending on the choice of the specificlabel.

As will be clear to the skilled person, another modification may involvethe introduction of a chelating group, for example to chelate one of themetals or metallic cations referred to above. Suitable chelating groupsfor example include, without limitation, diethyl-enetriaminepentaaceticacid (DTPA) or ethylenediaminetetraacetic acid (EDTA).

Yet another modification may comprise the introduction of a functionalgroup that is one part of a specific binding pair, such as thebiotin-(strept)avidin binding pair. Such a functional group may be usedto link the amino acid sequence, Nanobody®, compound or polypeptide ofthe invention to another protein, polypeptide or chemical compound thatis bound to the other half of the binding pair, i.e. through formationof the binding pair. For example, an amino acid sequence, Nanobody®,compound or polypeptide of the invention may be conjugated to biotin,and linked to another protein, polypeptide, compound or carrierconjugated to avidin or streptavidin. For example, such a conjugatedamino acid sequence, Nanobody®, compound or polypeptide of the inventionmay be used as a reporter, for example in a diagnostic system where adetectable signal-producing agent is conjugated to avidin orstreptavidin. Such binding pairs may for example also be used to bindthe amino acid sequence, Nanobody®, compound or polypeptide of theinvention to a carrier, including carriers suitable for pharmaceuticalpurposes. One non-limiting example are the liposomal formulationsdescribed by Cao and Suresh, Journal of Drug Targeting, 8, 4, 257(2000). Such binding pairs may also be used to link a therapeuticallyactive agent to the amino acid sequence, Nanobody®, compound orpolypeptide of the invention.

Other potential chemical and enzymatical modifications will be clear tothe skilled person. Such modifications may also be introduced forresearch purposes (e.g. to study function-activity relationships).Reference is for example made to Lundblad and Bradshaw, Biotechnol.Appl. Biochem., 26, 143-151 (1997).

Preferably, the derivatives are such that they bind to protein F ofhRSV, with an affinity (suitably measured and/or expressed as aK_(D)-value (actual or apparent), a K_(A)-value (actual or apparent), ak_(on)-rate and/or a k_(off)-rate, or alternatively as an IC₅₀ value, asfurther described herein) that is as defined herein (i.e. as defined forthe amino acid sequences, Nanobodies®, polypeptides or compounds perse). Such derivatives will usually also have a hRSV neutralizationefficacy and/or potency as defined herein.

As mentioned above, the invention also relates to proteins orpolypeptides that essentially consist of or comprise at least one aminoacid sequence, Nanobody®, compound or polypeptide of the invention. By“essentially consist of” is meant that the amino acid sequence of theprotein or polypeptide of the invention either is exactly the same asthe amino acid sequence, Nanobody®, compound or polypeptide of theinvention or corresponds to the amino acid sequence, Nanobody®, compoundor polypeptide of the invention which has a limited number of amino acidresidues, such as 1-20 amino acid residues, for example 1-10 amino acidresidues and preferably 1-6 amino acid residues, such as 1, 2, 3, 4, 5or 6 amino acid residues, added at the amino terminal end, at thecarboxy terminal end, or at both the amino terminal end and the carboxyterminal end of the amino acid sequence, Nanobody®, compound orpolypeptide.

Said amino acid residues may or may not change, alter or otherwiseinfluence the (biological) properties of the amino acid sequence,Nanobody®, compound or polypeptide of the invention and may or may notadd further functionality to the amino acid sequence, Nanobody®,compound or polypeptide. For example, such amino acid residues:

-   a) can comprise an N-terminal Met residue, for example as result of    expression in a heterologous host cell or host organism.-   b) may form a signal sequence or leader sequence that directs    secretion of the amino acid sequence, Nanobody®, compound or    polypeptide from a host cell upon synthesis. Suitable secretory    leader peptides will be clear to the skilled person, and may be as    further described herein. Usually, such a leader sequence will be    linked to the N-terminus of the amino acid sequence, Nanobody®,    compound or polypeptide, although the invention in its broadest    sense is not limited thereto;-   c) may form a sequence or signal that allows the amino acid    sequence, Nanobody®, compound or polypeptide to be directed towards    and/or to penetrate or enter into specific organs, tissues, cells,    or parts or compartments of cells, and/or that allows the amino acid    sequence, Nanobody®, compound or polypeptide to penetrate or cross a    biological barrier such as a cell membrane, a cell layer such as a    layer of epithelial cells, a tumor including solid tumors, or the    blood-brain-barrier. Examples of such amino acid sequences will be    clear to the skilled person. Some non-limiting examples are the    small peptide vectors (“Pep-trans vectors”) described in WO    03/026700 and in Temsamani et al., Expert Opin. Biol. Ther., 1, 773    (2001); Temsamani and Vidal, Drug Discov. Today, 9, 1012 (004) and    Rousseile, J. Pharmacal. Exp. Ther., 296, 124-131 (2001), and the    membrane translocator sequence described by Zhao et al., Apoptosis,    8, 631-637 (2003). C-terminal and N-terminal amino acid sequences    for intracellular targeting of antibody fragments are for example    described by Cardinale et al., Methods, 34, 171 (2004). Other    suitable techniques for intracellular targeting involve the    expression and/or use of so-called “intrabodies” comprising a amino    acid sequence, Nanobody®, compound or polypeptide of the invention,    as mentioned below;-   d) may form a “tag”, for example an amino acid sequence or residue    that allows or facilitates the purification of the amino acid    sequence, Nanobody®, compound or polypeptide, for example using    affinity techniques directed against said sequence or residue.    Thereafter, said sequence or residue may be removed (e.g. by    chemical or enzymatical cleavage) to provide the amino acid    sequence, Nanobody®, compound or polypeptide (for this purpose, the    tag may optionally be linked to the amino acid sequence, Nanobody®,    compound or polypeptide sequence via a cleavable linker sequence or    contain a cleavable motif). Some preferred, but non-limiting    examples of such residues are multiple histidine residues,    glutathione residues and a myc-tag such as AAAEQKLISEEDLNGAA (SEQ ID    NO: 111);-   e) may be one or more amino acid residues that have been    functionalized and/or that can serve as a site for attachment of    functional groups. Suitable amino acid residues and functional    groups will be clear to the skilled person and include, but are not    limited to, the amino acid residues and functional groups mentioned    herein for the derivatives of the amino acid sequences, Nanobodies®,    compounds or polypeptides of the invention.

The invention further relates to methods for preparing the amino acidsequences, Nanobodies®, polypeptides, compounds, nucleic acids, hostcells, products and compositions described herein.

The amino acid sequences, Nanobodies®, polypeptides, compounds andnucleic acids of the invention can be prepared in a manner known per se,as will be clear to the skilled person from the further descriptionherein. For example, the amino acid sequences, Nanobodies® andpolypeptides of the invention can be prepared in any manner known per sefor the preparation of antibodies and in particular for the preparationof antibody fragments (including but not limited to (single) domainantibodies and ScFv fragments). Some preferred, but non-limiting methodsfor preparing the amino acid sequences, Nanobodies®, polypeptides andnucleic acids include the methods and techniques described herein.

The method for producing an amino acid sequence of the invention, aNanobody® of the invention, a polypeptide of the invention, or amonovalent construct of the invention may comprise the following steps:

-   -   the expression, in a suitable host cell or host organism (also        referred to herein as a “host of the invention”) or in another        suitable expression system of a nucleic acid that encodes said        amino acid sequence, Nanobody® or polypeptide of the invention        (also referred to herein as a “nucleic acid of the invention”),

optionally followed by:

-   -   a isolating and/or purifying the amino acid sequence, Nanobody®        or polypeptide of the invention thus obtained.

In particular, such a method may comprise the steps of:

-   -   cultivating and/or maintaining a host of the invention under        conditions that are such that said host of the invention        expresses and/or produces at least one amino acid sequence,        Nanobody® and/or polypeptide of the invention;

optionally followed by:

-   -   isolating and/or purifying the amino acid sequence, Nanobody® or        polypeptide of the invention thus obtained.

Accordingly, the present invention also relates to a nucleic acid ornucleotide sequence that encodes an amino acid sequence, a Nanobody®, apolypeptide or a monovalent construct of the invention (also referred toas “nucleic acid of the invention” or “nucleotide sequence of theinvention”). A nucleic acid of the invention can be in the form ofsingle or double stranded DNA or RNA, and is preferably in the form ofdouble stranded DNA. For example, the nucleotide sequences of theinvention may be genomic DNA, cDNA or synthetic DNA (such as DNA with acodon usage that has been specifically adapted for expression in theintended host cell or host organism).

According to one embodiment of the invention, the nucleic acid of theinvention is in essentially isolated from, as defined herein. Thenucleic acid of the invention may also be in the form of, be present inand/or be part of a vector, such as for example a plasmid, cosmid orYAC, which again may be in essentially isolated form.

The nucleic acids of the invention can be prepared or obtained in amanner known per se, based on the information on the amino acidsequences, Nanobodies® and/or polypeptides of the invention givenherein, and/or can be isolated from a suitable natural source. Also, aswill be clear to the skilled person, to prepare a nucleic acid of theinvention, also several nucleotide sequences, such as at least onenucleotide sequence encoding an amino acid sequence or Nanobody® and forexample nucleic acids encoding one or more linkers can be linkedtogether in a suitable manner.

Techniques for generating the nucleic acids of the invention will beclear to the skilled person and may for instance include, but are notlimited to, automated DNA synthesis; site-directed mutagenesis;combining two or more naturally occurring and/or synthetic sequences (ortwo or more parts thereof), introduction of mutations that lead to theexpression of a truncated expression product; introduction of one ormore restriction sites (e.g. to create cassettes and/or regions that mayeasily be digested and/or ligated using suitable restriction enzymes),and/or the introduction of mutations by means of a PCR reaction usingone or more “mismatched” primers. These and other techniques will beclear to the skilled person, and reference is again made to the standardhandbooks, such as Sambrook et al. and Ausubel et al., mentioned above,as well as the Examples below.

The nucleic acid of the invention may also be in the form of, be presentin and/or be part of a genetic construct, as will be clear to the personskilled in the art. Such genetic constructs generally comprise at leastone nucleic acid of the invention that is optionally linked to one ormore elements of genetic constructs known per se, such as for exampleone or more suitable regulatory elements (such as a suitablepromoter(s), enhancer(s), terminator(s), etc.) and the further elementsof genetic constructs referred to herein. Such genetic constructscomprising at least one nucleic acid of the invention will also bereferred to herein as “genetic constructs of the invention”.

The genetic constructs of the invention may be DNA or RNA, and arepreferably double-stranded DNA. The genetic constructs of the inventionmay also be in a form suitable for transformation of the intended hostcell or host organism, in a form suitable for integration into thegenomic DNA of the intended host cell or in a form suitable forindependent replication, maintenance and/or inheritance in the intendedhost organism. For instance, the genetic constructs of the invention maybe in the form of a vector, such as for example a plasmid, cosmid, YAC,a viral vector or transposon. In particular, the vector may be anexpression vector, i.e. a vector that can provide for expression invitro and/or in vivo (e.g. in a suitable host cell, host organism and/orexpression system).

In a preferred but non-limiting embodiment, a genetic construct of theinvention comprises

a) at least one nucleic acid of the invention; operably connected to

b) one or more regulatory elements, such as a promoter and optionally asuitable terminator; and optionally also

c) one or more further elements of genetic constructs known per se;

in which the terms “regulatory element”, “promoter”, “terminator” and“operably connected” have their usual meaning in the art (as furtherdescribed herein); and in which said “further elements” present in thegenetic constructs may for example be 3′- or 5′-UTR sequences, leadersequences, selection markers, expression markers/reporter genes, and/orelements that may facilitate or increase (the efficiency of)transformation or integration. These and other suitable elements forsuch genetic constructs will be clear to the skilled person, and may forinstance depend upon the type of construct used; the intended host cellor host organism; the manner in which the nucleotide sequences of theinvention of interest are to be expressed (e.g. via constitutive,transient or inducible expression); and/or the transformation techniqueto be used. For example, regulatory sequences, promoters and terminatorsknown per se for the expression and production of antibodies andantibody fragments (including but not limited to (single) domainantibodies and ScFv fragments) may be used in an essentially analogousmanner.

Preferably, in the genetic constructs of the invention, said at leastone nucleic acid of the invention and said regulatory elements, andoptionally said one or more further elements, are “operably linked” toeach other, by which is generally meant that they are in a functionalrelationship with each other. For instance, a promoter is considered“operably linked” to a coding sequence if said promoter is able toinitiate or otherwise control/regulate the transcription and/or theexpression of a coding sequence (in which said coding sequence should beunderstood as being “under the control of” said promoter). Generally,when two nucleotide sequences are operably linked, they will be in thesame orientation and usually also in the same reading frame. They willusually also be essentially contiguous, although this may also not berequired.

Preferably, the regulatory and further elements of the geneticconstructs of the invention are such that they are capable of providingtheir intended biological function in the intended host cell or hostorganism.

For instance, a promoter, enhancer or terminator should be “operable” inthe intended host cell or host organism, by which is meant that (forexample) said promoter should be capable of initiating or otherwisecontrolling/regulating the transcription and/or the expression of anucleotide sequence—e.g. a coding sequence—to which it is operablylinked (as defined herein).

Some particularly preferred promoters include, but are not limited to,promoters known per se for the expression in the host cells mentionedherein; and in particular promoters for the expression in the bacterialcells, such as those mentioned herein and/or those used in the Examples.

A selection marker should be such that it allows—i.e. under appropriateselection conditions—host cells and/or host organisms that have been(successfully) transformed with the nucleotide sequence of the inventionto be distinguished from host cells/organisms that have not been(successfully) transformed. Some preferred, but non-limiting examples ofsuch markers are genes that provide resistance against antibiotics (suchas kanamycin or ampicillin), genes that provide for temperatureresistance, or genes that allow the host cell or host organism to bemaintained in the absence of certain factors, compounds and/or (food)components in the medium that are essential for survival of thenon-transformed cells or organisms.

A leader sequence should be such that—in the intended host cell or hostorganism—it allows for the desired post-translational modificationsand/or such that it directs the transcribed mRNA to a desired part ororganelle of a cell. A leader sequence may also allow for secretion ofthe expression product from said cell. As such, the leader sequence maybe any pro-, pre-, or prepro-sequence operable in the host cell or hostorganism. Leader sequences may not be required for expression in abacterial cell. For example, leader sequences known per se for theexpression and production of antibodies and antibody fragments(including but not limited to single domain antibodies and ScFvfragments) may be used in an essentially analogous manner.

An expression marker or reporter gene should be such that—in the hostcell or host organism—it allows for detection of the expression of (agene or nucleotide sequence present on) the genetic construct. Anexpression marker may optionally also allow for the localisation of theexpressed product, e.g. in a specific part or organelle of a cell and/orin (a) specific cell(s), tissue(s), organ(s) or part(s) of amulticellular organism. Such reporter genes may also be expressed as aprotein fusion with the amino acid sequence, Nanobody® or polypeptide ofthe invention. Some preferred, but non-limiting examples includefluorescent proteins such as GFP.

Some preferred, but non-limiting examples of suitable promoters,terminator and further elements include those that can be used for theexpression in the host cells mentioned herein; and in particular thosethat are suitable for expression in bacterial cells, such as thosementioned herein and/or those used in the Examples below. For some(further) non-limiting examples of the promoters, selection markers,leader sequences, expression markers and further elements that may bepresent/used in the genetic constructs of the invention—such asterminators, transcriptional and/or translational enhancers and/orintegration factors—reference is made to the general handbooks such asSambrook et al. and Ausubel et al. mentioned above, as well as to theexamples that are given in WO 95/07463, WO 96/23810, WO 95/07463, WO95/21191, WO 97/11094, WO 97/42320, WO 98/06737, WO 98/21355, U.S. Pat.No. 7,207,410, U.S. Pat. No. 5,693,492 and EP 1 085 089. Other exampleswill be clear to the skilled person. Reference is also made to thegeneral background art cited above and the further references citedherein.

The genetic constructs of the invention may generally be provided bysuitably linking the nucleotide sequence(s) of the invention to the oneor more further elements described above, for example using thetechniques described in the general handbooks such as Sambrook et al.and Ausubel et al., mentioned above.

Often, the genetic constructs of the invention will be obtained byinserting a nucleotide sequence of the invention in a suitable(expression) vector known per se. Some preferred, but non-limitingexamples of suitable expression vectors are those used in the Examplesbelow, as well as those mentioned herein.

The nucleic acids of the invention and/or the genetic constructs of theinvention may be used to transform a host cell or host organism, i.e.for expression and/or production of the amino acid sequence, Nanobody®or polypeptide of the invention. Suitable hosts or host cells will beclear to the skilled person, and may for example be any suitable fungal,prokaryotic or eukaryotic cell or cell line or any suitable fungal,prokaryotic or eukaryotic organism, for example:

-   -   a bacterial strain, including but not limited to gram-negative        strains such as strains of Escherichia coli; of Proteus, for        example of Proteus mirabilis; of Pseudomonas, for example of        Pseudomonas fluorescens; and gram-positive strains such as        strains of Bacillus, for example of Bacillus subtilis or of        Bacillus brevis; of Streptomyces, for example of Streptomyces        lividans; of Staphylococcus, for example of Staphylococcus        carnosus; and of Lactococcus, for example of Lactococcus lactis;    -   a fungal cell, including but not limited to cells from species        of Trichoderma, for example from Trichoderma reesei; of        Neurospora, for example from Neurospora crassa; of Sordaria, for        example from Sordaria macrospora; of Aspergillus, for example        from Aspergillus niger or from Aspergillus sojae; or from other        filamentous fungi;    -   a yeast cell, including but not limited to cells from species of        Saccharomyces, for example of Saccharomyces cerevisiae; of        Schizosaccharomyces, for example of Schizosaccharomyces pombe;        of Pichia, for example of Pichia pastoris or of Pichia        methanolica; of Hansenula, for example of Hansenula polymorpha;        of Kluyveromyces, for example of Kluyveromyces lactis; of        Arxula, for example of Arxula adeninivorans; of Yarrowia, for        example of Yarrowia lipolytica;    -   an amphibian cell or cell line, such as Xenopus oocytes;    -   an insect-derived cell or cell line, such as cells/cell lines        derived from lepidoptera, including but not limited to        Spodoptera SF9 and Sf21 cells or cells/cell lines derived from        Drosophila, such as Schneider and Kc cells;    -   a plant or plant cell, for example in tobacco plants; and/or    -   a mammalian cell or cell line, for example a cell or cell line        derived from a human, a cell or a cell line from mammals        including but not limited to CHO-cells, BHK-cells (for example        BILK-21 cells) and human cells or cell lines such as HeLa, COS        (for example COS-7) and PER.C6 cells;        as well as all other hosts or host cells known per se for the        expression and production of antibodies and antibody fragments        (including but not limited to (single) domain antibodies and        ScFv fragments), which will be clear to the skilled person.        Reference is also made to the general background art cited        hereinabove, as well as to for example WO 94/29457; WO 96/34103;        WO 99/42077; Frenken et al., (1998), supra; Riechmann and        Muyldermans, (1999), supra; van der Linden, (2000), supra;        Thomassen et al., (2002), supra; Joosten et al., (2003), supra;        Joosten et al., (2005), supra; and the further references cited        herein.

The amino acid sequences, Nanobodies® and polypeptides of the inventioncan also be introduced and expressed in one or more cells, tissues ororgans of a multicellular organism, for example for prophylactic and/ortherapeutic purposes (e.g. as a gene therapy). For this purpose, thenucleotide sequences of the invention may be introduced into the cellsor tissues in any suitable way, for example as such (e.g. usingliposomes) or after they have been inserted into a suitable gene therapyvector (for example derived from retroviruses such as adenovirus, orparvoviruses such as adeno-associated virus). As will also be clear tothe skilled person, such gene therapy may be performed in vivo and/or insitu in the body of a patient by administering a nucleic acid of theinvention or a suitable gene therapy vector encoding the same to thepatient or to specific cells or a specific tissue or organ of thepatient; or suitable cells (often taken from the body of the patient tobe treated, such as explanted lymphocytes, bone marrow aspirates ortissue biopsies) may be treated in vitro with a nucleotide sequence ofthe invention and then be suitably (re-)introduced into the body of thepatient. All this can be performed using gene therapy vectors,techniques and delivery systems which are well known to the skilledperson, and for example described in Culver, K. W., “Gene Therapy”,1994, p. xii, Mary Ann Liebert, Inc., Publishers, New York, N.Y.);Giordano, Nature F Medicine 2 (1996), 534-539; Schaper, Circ. Res. 79(1996), 911-919; Anderson, Science 256 (1992), 808-813; Verma, Nature389 (1994), 239; Isner, Lancet 348 (1996), 370-374; Muhlhauser, Circ.Res. 77 (1995), 4077-1086; Onodera, Blood 91; (1998), 30-36; Verma, GeneTher. 5 (1998), 692-699; Nabel, Ann. N.Y. Acad. Sci.: 811 (1997),289-292; Verzeletti, Hum. Gene Ther. 9 (1998), 2243-51; Wang, NatureMedicine 2 (1996), 714-716; WO 94/29469; WO 97/00957, U.S. Pat. No.5,580,859; U.S. Pat. No. 5,589,466; or Schaper, Current Opinion inBiotechnology 7 (1996), 635-640. For example, in situ expression of ScFvfragments (Afanasieva et al., Gene Ther., 10, 1850-1859 (2003)) and ofdiabodies (Blanco et al., J. Immunol, 171, 1070-1077 (2003)) has beendescribed in the art.

For expression of the amino acid sequences, Nanobodies® or polypeptidesin a cell, they may also be expressed as so-called “intrabodies”, as forexample described in WO 94/02610, WO 95/22618 and U.S. Pat. No.7,004,940; WO 03/014960; in Cattaneo, A. & Biocca, S. (1997)Intracellular Antibodies: Development and Applications. Landes andSpringer-Verlag; and in Kontermann, Methods 34, (2004), 163-170.

The amino add sequences, Nanobodies® and polypeptides of the inventioncan for example also be produced in the milk of transgenic mammals, forexample in the milk of rabbits, cows, goats or sheep (see for exampleU.S. Pat. No. 6,741,957, U.S. Pat. No. 6,304,489 and U.S. Pat. No.6,849,992 for general techniques for introducing transgenes intomammals), in plants or parts of plants including but not limited totheir leaves, flowers, fruits, seed, roots or turbers (for example intobacco, maize, soybean or alfalfa) or in for example pupae of thesilkworm Bombix mori.

Furthermore, the amino acid sequences, Nanobodies® and polypeptides ofthe invention can also be expressed and/or produced in cell-freeexpression systems, and suitable examples of such systems will be clearto the skilled person. Some preferred, but non-limiting examples includeexpression in the wheat germ system; in rabbit reticulocyte lysates; orin the E. coli Zubay system.

As mentioned above, one of the advantages of the use of Nanobodies® isthat the polypeptides based thereon can be prepared through expressionin a suitable bacterial system, and suitable bacterial expressionsystems, vectors, host cells, regulatory elements, etc., will be clearto the skilled person, for example from the references cited above. Itshould however be noted that the invention in its broadest sense is notlimited to expression in bacterial systems.

Preferably, in the invention, an (in vivo or in vitro) expressionsystem, such as a bacterial expression system, is used that provides thepolypeptides of the invention in a form that is suitable forpharmaceutical use, and such expression systems will again be clear tothe skilled person. As also will be clear to the skilled person,polypeptides of the invention suitable for pharmaceutical use can beprepared using techniques for peptide synthesis.

For production on industrial scale, preferred heterologous hosts for the(industrial) production of Nanobodies® or Nanobody®-containing proteintherapeutics include strains of E. coli, Pichia pastoris, S. cerevisiaethat are suitable for large scale expression/production/fermentation,and in particular for large scale pharmaceuticalexpression/production/fermentation. Suitable examples of such strainswill be clear to the skilled person. Such strains andproduction/expression systems are also made available by companies suchas Biovitrum (Uppsala, Sweden).

Alternatively, mammalian cell lines, in particular Chinese hamster ovary(CHO) cells, can be used for large scaleexpression/production/fermentation, and in particular for large scalepharmaceutical expression/production/fermentation. Again, suchexpression/production systems are also made available by some of thecompanies mentioned above.

The choice of the specific expression system would depend in part on therequirement for certain post-translational modifications, morespecifically glycosylation. The production of a Nanobody®-containingrecombinant protein for which glycosylation is desired or required wouldnecessitate the use of mammalian expression hosts that have the abilityto glycosylate the expressed protein. In this respect, it will be clearto the skilled person that the glycosylation pattern obtained (i.e. thekind, number and position of residues attached) will depend on the cellor cell line that is used for the expression. Preferably, either a humancell or cell line is used (i.e. leading to a protein that essentiallyhas a human glycosylation pattern) or another mammalian cell line isused that can provide a glycosylation pattern that is essentially and/orfunctionally the same as human glycosylation or at least mimics humanglycosylation. Generally, prokaryotic hosts such as E. coli do not havethe ability to glycosylate proteins, and the use of lower eukaryotessuch as yeast usually leads to a glycosylation pattern that differs fromhuman glycosylation. Nevertheless, it should be understood that all theforegoing host cells and expression systems can be used in theinvention, depending on the desired amino acid sequence, Nanobody® orpolypeptide to be obtained.

Thus, according to one non-limiting embodiment of the invention, theamino acid sequence, Nanobody® or polypeptide of the invention isglycosylated. According to another non-limiting embodiment of theinvention, the amino acid sequence, Nanobody® or polypeptide of theinvention is non-glycosylated.

According to one preferred, but non-limiting embodiment of theinvention, the amino acid sequence, Nanobody® or polypeptide of theinvention is produced in a bacterial cell, in particular a bacterialcell suitable for large scale pharmaceutical production, such as cellsof the strains mentioned above.

According to another preferred, but non-limiting embodiment of theinvention, the amino acid sequence, Nanobody® or polypeptide of theinvention is produced in a yeast cell, in particular a yeast cellsuitable for large scale pharmaceutical production, such as cells of thespecies mentioned above.

According to yet another preferred, but non-limiting embodiment of theinvention, the amino acid sequence, Nanobody® or polypeptide of theinvention is produced in a mammalian cell, in particular in a human cellor in a cell of a human cell line, and more in particular in a humancell or in a cell of a human cell line that is suitable for large scalepharmaceutical production, such as the cell lines mentioned hereinabove.

When expression in a host cell is used to produce the amino acidsequences, Nanobodies® and the polypeptides of the invention, the aminoacid sequences, Nanobodies® and polypeptides of the invention can beproduced either intracellularly (e.g. in the cytosol, in the periplasmaor in inclusion bodies) and then isolated from the host cells andoptionally further purified; or can be produced extracellularly (e.g. inthe medium in which the host cells are cultured) and then isolated fromthe culture medium and optionally further purified. When eukaryotic hostcells are used, extracellular production is usually preferred since thisconsiderably facilitates the further isolation and downstream processingof the amino acid sequences, Nanobodies®, polypeptides and proteinsobtained. Bacterial cells such as the strains of E. coli mentioned abovenormally do not secrete proteins extracellularly, except for a fewclasses of proteins such as toxins and hemolysin, and secretoryproduction in E. coli refers to the translocation of proteins across theinner membrane to the periplasmic space. Periplasmic production providesseveral advantages over cytosolic production. For example, theN-terminal amino acid sequence of the secreted product can be identicalto the natural gene product after cleavage of the secretion signalsequence by a specific signal peptidase. Also, there appears to be muchless protease activity in the periplasm than in the cytoplasm. Inaddition, protein purification is simpler due to fewer contaminatingproteins in the periplasm. Another advantage is that correct disulfidebonds may form because the periplasm provides a more oxidativeenvironment than the cytoplasm. Proteins overexpressed in E. coli areoften found in insoluble aggregates, so-called inclusion bodies. Theseinclusion bodies may be located in the cytosol or in the periplasm; therecovery of biologically active proteins from these inclusion bodiesrequires a denaturation/refolding process. Many recombinant proteins,including therapeutic proteins, are recovered from inclusion bodies.Alternatively, as will be clear to the skilled person, recombinantstrains of bacteria that have been genetically modified so as to secretea desired protein, and in particular an amino acid sequence, Nanobody®or a polypeptide of the invention, can be used.

Thus, according to one non-limiting embodiment of the invention, theamino acid sequence, Nanobody® or polypeptide of the invention is anamino acid sequence, Nanobody® or polypeptide that has been producedintracellularly and that has been isolated from the host cell, and inparticular from a bacterial cell or from an inclusion body in abacterial cell. According to another non-limiting embodiment of theinvention, the amino acid sequence, Nanobody® or polypeptide of theinvention is an amino acid sequence, Nanobody® or polypeptide that hasbeen produced extracellularly, and that has been isolated from themedium in which the host cell is cultivated.

Some preferred, but non-limiting promoters for use with these host cellsinclude,

-   -   for expression in E. coli: lac promoter (and derivatives thereof        such as the lacUV5 promoter); arabinose promoter; left-(PL) and        rightward (PR) promoter of phage lambda; promoter of the trp        operon; hybrid lac/trp promoters (tac and trc); T7-promoter        (more specifically that of T7-phage gene 10) and other T-phage        promoters; promoter of the Tn10 tetracycline resistance gene;        engineered variants of the above promoters that include one or        more copies of an extraneous regulatory operator sequence;    -   for expression in S. cerevisiae: constitutive: ADH1 (alcohol        dehydrogenase 1), ENO (enolase), CYC1 (cytochrome c iso-1),        GAPDH (glyceraldehydes-3-phosphate dehydrogenase), PGK1        (phosphoglycerate kinase), PYK1 (pyruvate kinase); regulated:        GAL1,10,7 (galactose metabolic enzymes), ADH2 (alcohol        dehydrogenase 2), PHO5 (acid phosphatase), CUP1 (copper        metallothionein); heterologous: CaMV (cauliflower mosaic virus        355 promoter);    -   for expression in Pichia pastoris: the AOX1 promoter (alcohol        oxidase I);    -   for expression in mammalian cells: human cytomegalovirus (hCMV)        immediate early enhancer/promoter; human cytomegalovirus (hCMV)        immediate early promoter variant that contains two tetracycline        operator sequences such that the promoter can be regulated by        the Tet repressor; Herpes Simplex Virus thymidine kinase (TK)        promoter; Rous Sarcoma Virus long terminal repeat (RSV LTR)        enhancer/promoter; elongation factor 1α (hEF-1α) promoter from        human, chimpanzee, mouse or rat; the SV40 early promoter; HIV-1        long terminal repeat promoter; β-actin promoter;

Some preferred, but non-limiting vectors for use with these host cellsinclude:

-   -   vectors for expression in mammalian cells: pMAMneo (Clontech),        pcDNA3 (Invitrogen), pMC1neo (Stratagene), pSG5 (Stratagene),        EBO-pSV2-neo (ATCC 37593), pBPV-1 (8-2) (ATCC 37110),        pdBPV-MMTneo (342-12) (ATCC 37224), pRSVgpt (ATCC37199), pRSVneo        (ATCC37198), pSV2-dhfr (ATCC 37146), pUCTag (ATCC 37460) and        1ZD35 (ATCC 37565), as well as viral-based expression systems,        such as those based on adenovirus;    -   vectors for expression in bacterial cells: pET vectors (Novagen)        and pQE vectors (Qiagen);    -   vectors for expression in yeast or other fungal cells: pYES2        (Invitrogen) and Pichia expression vectors (Invitrogen);    -   vectors for expression in insect cells: pBlueBacII (Invitrogen)        and other baculovirus vectors vectors for expression in plants        or plant cells: for example vectors based on cauliflower mosaic        virus or tobacco mosaic virus, suitable strains of        Agrobacterium, or Ti-plasmid based vectors.

Some preferred, but non-limiting secretory sequences for use with thesehost cells include:

-   -   for use in bacterial cells such as E. coli: PeIB, BIa, OmpA,        OmpC, OmpF, OmpT, SU, PhoA, PhoE, MalE, Lpp, LamB, and the like;        TAT signal peptide, hemolysin C-terminal secretion signal;    -   for use in yeast: α-mating factor prepro-sequence, phosphatase        (pho1), invertase (Suc), etc.;    -   for use in mammalian cells: indigenous signal in case the target        protein is of eukaryotic origin; murine Ig κ-chain V-J2-C signal        peptide; etc.

Suitable techniques for transforming a host or host cell of theinvention will be clear to the skilled person and may depend on theintended host cell/host organism and the genetic construct to be used.Reference is again made to the handbooks and patent applicationsmentioned above.

After transformation, a step for detecting and selecting those hostcells or host organisms that have been successfully transformed with thenucleotide sequence/genetic construct of the invention may be performed.This may for instance be a selection step based on a selectable markerpresent in the genetic construct of the invention or a step involvingthe detection of the amino acid sequence of the invention, e.g. usingspecific antibodies.

The transformed host cell (which may be in the form or a stable cellline) or host organisms (which may be in the form of a stable mutantline or strain) farm further aspects of the present invention.

Preferably, these host cells or host organisms are such that theyexpress, or are (at least) capable of expressing (e.g. under suitableconditions), an amino acid sequence, Nanobody® or polypeptide of theinvention (and in case of a host organism: in at least one cell, part,tissue or organ thereof). The invention also includes furthergenerations, progeny and/or offspring of the host cell or host organismof the invention, that may for instance be obtained by cell division orby sexual or asexual reproduction.

To produce/obtain expression of the amino acid sequences, Nanobodies® orpolypeptides of the invention, the transformed host cell or transformedhost organism may generally be kept, maintained and/or cultured underconditions such that the (desired) amino acid sequence, Nanobody® orpolypeptide of the invention is expressed/produced. Suitable conditionswill be clear to the skilled person and will usually depend upon thehost cell/host organism used, as well as on the regulatory elements thatcontrol the expression of the (relevant) nucleotide sequence of theinvention. Again, reference is made to the handbooks and patentapplications mentioned above in the paragraphs on the genetic constructsof the invention.

Generally, suitable conditions may include the use of a suitable medium,the presence of a suitable source of food and/or suitable nutrients, theuse of a suitable temperature, and optionally the presence of a suitableinducing factor or compound (e.g. when the nucleotide sequences of theinvention are under the control of an inducible promoter); all of whichmay be selected by the skilled person. Again, under such conditions, theamino acid sequences of the invention may be expressed in a constitutivemanner, in a transient manner, or only when suitably induced.

It will also be clear to the skilled person that the amino acidsequence, Nanobody® or polypeptide of the invention may (first) begenerated in an immature form (as mentioned above), which may then besubjected to post-translational modification, depending on the hostcell/host organism used. Also, the amino acid sequence, Nanobody® orpolypeptide of the invention may be glycosylated, again depending on thehost cell/host organism used.

The amino acid sequence, Nanobody® or polypeptide of the invention maythen be isolated from the host cell/host organism and/or from the mediumin which said host cell or host organism was cultivated, using proteinisolation and/or purification techniques known per se, such as(preparative) chromatography and/or electrophoresis techniques,differential precipitation techniques, affinity techniques (e.g. using aspecific, cleavable amino acid sequence fused with the amino acidsequence, Nanobody® or polypeptide of the invention) and/or preparativeimmunological techniques (i.e. using antibodies against the amino acidsequence to be isolated).

The invention further relates to a product or composition containing orcomprising at least one amino acid sequence of the invention (or asuitable fragment thereof), at least one Nanobody® of the invention, atleast one polypeptide of the invention, at least one compound orconstruct of the invention, at least one monovalent construct of theinvention and/or at least one nucleic acid of the invention, andoptionally one or more further components of such compositions known perse, i.e. depending on the intended use of the composition. Such aproduct or composition may for example be a pharmaceutical composition(as described herein), a veterinary composition or a product orcomposition for diagnostic use (as also described herein). Somepreferred but non-limiting examples of such products or compositionswill become clear from the further description herein.

Generally, for pharmaceutical use, the amino acid sequences, Nanobodies®and polypeptides of the invention may be formulated as a pharmaceuticalpreparation or compositions comprising at least one amino acid sequence,Nanobody® or polypeptide of the invention and at least onepharmaceutically acceptable carrier, diluent or excipient and/oradjuvant, and optionally one or more further pharmaceutically activepolypeptides and/or compounds. By means of non-limiting examples, such aformulation may be in a form suitable for oral administration, forparenteral administration (such as by intravenous, intramuscular orsubcutaneous injection or intravenous infusion), for topicaladministration, for administration by inhalation, by a skin patch, by animplant, by a suppository, etc. Such suitable administration forms—whichmay be solid, semi-solid or liquid, depending on the manner ofadministration—as well as methods and carriers for use in thepreparation thereof, will be clear to the skilled person, and arefurther described herein.

Thus, in a further aspect, the invention relates to a pharmaceuticalcomposition that contains at least one amino acid of the invention, atleast one Nanobody® of the invention, at least one compound or constructof the invention or at least one polypeptide of the invention and atleast one suitable carrier, diluent or excipient (i.e. suitable forpharmaceutical use), and optionally one or more further activesubstances.

Generally, the amino acid sequences, Nanobodies®, compounds, constructsand polypeptides of the invention can be formulated and administered inany suitable manner known per se, for which reference is for examplemade to the general background art cited above (and in particular to WO04/041862, WO 04/041863, WO 04/041865, WO 04/041867 and WO 08/020,079)as well as to the standard handbooks, such as Remington's PharmaceuticalSciences, 18^(th) Ed., Mack Publishing Company, USA (1990), Remington,the Science and Practice of Pharmacy, 21 st Edition, Lippincott Williamsand Wilkins (2005); or the Handbook of Therapeutic Antibodies (S. Dubel,Ed.), Wiley, Weinheim, 2007 (see for example pages 252-255).

For example, the amino acid sequences, Nanobodies®, compounds,constructs and polypeptides of the invention may be formulated andadministered in any manner known per se for conventional antibodies andantibody fragments (including ScFv's and diabodies) and otherpharmaceutically active proteins. Such formulations and methods forpreparing the same will be clear to the skilled person, and for exampleinclude preparations suitable for parenteral administration (for exampleintravenous, intraperitoneal, subcutaneous, intramuscular, intraluminal,intra-arterial or intrathecal administration) or for topical (i.e.transdermal or intradermal) administration.

Preparations for parenteral administration may for example be sterilesolutions, suspensions, dispersions or emulsions that are suitable forinfusion or injection. Suitable carriers or diluents for suchpreparations for example include, without limitation, those mentioned onpage 143 of WO 08/020,079. Usually, aqueous solutions or suspensionswill be preferred.

The amino acid sequences, Nanobodies®, compounds, constructs andpolypeptides of the invention can also be administered using genetherapy methods of delivery. See, e.g., U.S. Pat. No. 5,399,346, whichis incorporated by reference in its entirety. Using a gene therapymethod of delivery, primary cells transfected with the gene encoding anamino acid sequence, Nanobody® or polypeptide of the invention canadditionally be transfected with tissue specific promoters to targetspecific organs, tissue, grafts, tumors, or cells and can additionallybe transfected with signal and stabilization sequences for subcelluiarlylocalized expression.

Thus, the amino acid sequences, Nanobodies®, compounds, constructs andpolypeptides of the invention may be systemically administered, e.g.,orally, in combination with a pharmaceutically acceptable vehicle suchas an inert diluent or an assimilable edible carrier. They may beenclosed in hard or soft shell gelatin capsules, may be compressed intotablets, or may be incorporated directly with the food of the patient'sdiet. For oral therapeutic administration, the amino acid sequences,Nanobodies®, compounds, constructs and polypeptides of the invention maybe combined with one or more excipients and used in the form ofingestible tablets, buccal tablets, troches, capsules, elixirs,suspensions, syrups, wafers, and the like. Such compositions andpreparations should contain at least 0.1% of the amino acid sequence,Nanobody®, compound, construct or polypeptide of the invention. Theirpercentage in the compositions and preparations may, of course, bevaried and may conveniently be between about 2 to about 60% of theweight of a given unit dosage form. The amount of the amino acidsequence, Nanobody®, compound, construct or polypeptide of the inventionin such therapeutically useful compositions is such that an effectivedosage level will be obtained.

The tablets, troches, pilis, capsules, and the like may also containbinders, excipients, disintegrating agents, lubricants and sweetening orflavouring agents, for example those mentioned on pages 143-144 of WO08/020,079. When the unit dosage form is a capsule, it may contain, inaddition to materials of the above type, a liquid carrier, such as avegetable oil or a polyethylene glycol. Various other materials may bepresent as coatings or to otherwise modify the physical form of thesolid unit dosage form. For instance, tablets, pills, or capsules may becoated with gelatin, wax, shellac or sugar and the like. A syrup orelixir may contain the amino acid sequences, Nanobodies®, compounds,constructs and polypeptides of the invention, sucrose or fructose as asweetening agent, methyl and propylparabens as preservatives, a dye andflavoring such as cherry or orange flavor. Of course, any material usedin preparing any unit dosage form should be pharmaceutically acceptableand substantially non-toxic in the amounts employed. In addition, theamino acid sequences, Nanobodies®, compounds, constructs andpolypeptides of the invention may be incorporated into sustained-releasepreparations and devices.

Preparations and formulations for oral administration may also beprovided with an enteric coating that will allow the constructs of theinvention to resist the gastric environment and pass into theintestines. More generally, preparations and formulations for oraladministration may be suitably formulated for delivery into any desiredpart of the gastrointestinal tract. In addition, suitable suppositoriesmay be used for delivery into the gastrointestinal tract.

The amino acid sequences, Nanobodies®, compounds, constructs andpolypeptides of the invention may also be administered intravenously orintraperitoneally by infusion or injection, as further described onpages 144 and 145 of WO 08/020,079.

For topical administration, the amino acid sequences, Nanobodies®,compounds, constructs and polypeptides of the invention may be appliedin pure form, i.e., when they are liquids. However, it will generally bedesirable to administer them to the skin as compositions orformulations, in combination with a dermatologically acceptable carrier,which may be a solid or a liquid, as further described on page 145 of WO08/020,079.

Generally, the concentration of the amino acid sequences, Nanobodies®,compounds, constructs and polypeptides of the invention in a liquidcomposition, such as a lotion, will be from about 0.1-25 wt-%,preferably from about 0.5-10 wt-%. The concentration in a semi-solid orsolid composition such as a gel or a powder will be about 0.1-5 wt-%,preferably about 0.5-2.5 wt-%.

In a preferred aspect, the amino acid sequences, Nanobodies®, compounds,constructs and/or polypeptides of the invention and/or compositionscomprising the same are administered to the pulmonary tissue. In thecontext of the present invention, “pulmonary tissue” is for the purposesof this invention equivalent with lung tissue or lung. The lungcomprises 2 distinct zones: a conducting and a respiratory zone, withinwhich the airway and vascular compartments lie (see e.g. “Pulmonary DrugDelivery”, Edited by Karoline Bechtold-Peters and Henrik Luessen, 2007,ISBN 978-3-87193-322-6 pages 16-28).

For pulmonary delivery, the amino acid sequences, Nanobodies®,compounds, constructs and polypeptides of the invention may be appliedin pure form, i.e., when they are liquids or a dry powder. However, itwill be preferred to administer them to the pulmonary tissue ascomposition or formulation comprising an amino acid sequence, Nanobody®,compound, construct and/or polypeptide of the invention and a carriersuitable for pulmonary delivery. Accordingly the present invention alsorelates to a pharmaceutical composition comprising the amino acidsequence, Nanobody®, compound, construct and/or polypeptide of theinvention and a carrier suitable for pulmonary delivery. Carrierssuitable for pulmonary delivery are known in the art.

The amino acid sequences, Nanobodies®, compounds, constructs and/orpolypeptides of the invention may also be administered as micro- ornanoparticles of pure drugs with particle sizes and distributionsfavorable for pulmonary delivery.

Accordingly the present invention also relates to a pharmaceuticaldevice suitable for the pulmonary delivery of the amino acid sequences,Nanobodies®, compounds, constructs and/or polypeptides of the inventionand suitable in the use of a composition comprising the same. Thisdevice may be an inhaler for liquids (e.g. a suspension of fine solidparticles or droplets) comprising the amino acid sequence, Nanobody®,compound, constructs and/or polypeptide of the invention. Preferablythis device is an aerosol comprising the amino acid sequence, Nanobody®,compound, construct and/or polypeptide of the invention. The device mayalso be a dry powder inhaler comprising the amino acid sequence,Nanobody®, compound, construct and/or polypeptide of the invention inthe form of a dry powder.

In a preferred method, the administration to the pulmonary tissue isperformed by inhaling the amino acid sequences, Nanobodies®, compounds,constructs and/or polypeptides of the invention and/or the compositioncomprising the same in an aerosol cloud. According to the invention,inhaling of the aerosol cloud can be performed by an inhaler device. Thedevice should generate from a formulation comprising the amino acidsequences, Nanobodies®, compounds, constructs and/or polypeptides of theinvention (and/or composition comprising the same) an aerosol cloud ofthe desired particle size (distribution) at the appropriate moment ofthe mammal's inhalation cycle, containing the right dose of the aminoacid sequences, Nanobodies®, compounds, constructs and/or polypeptidesof the invention (“Pulmonary drug delivery”, Bechtold-Peters andLuessen, eds., ISBN 978-3-87193-322-6, page 125).

In the context of the present invention, “aerosol” denotes a suspensionof fine solid particles or liquid droplets (or combination thereof) in agas wherein for the purposes of this invention the particles and/ordroplets comprise the amino acid sequences, Nanobodies®, compounds,constructs and/or polypeptides of the invention.

The device should generate from the formulation an aerosol cloud of thedesired particle size (distribution) at the appropriate moment of themammal's inhalation cycle, containing the right dose of amino acidsequences, Nanobodies®, compounds, constructs and/or polypeptides of theinvention. The following 4 requirements (formulation, particle size,time and dose) should be considered (“Pulmonary Drug Delivery”,Bechtold-Peters and Luessen, eds., supra, pages 125 and 126):

-   -   The formulations that are used in the devices may vary from        aqueous solutions or suspensions used in nebulizers to the        propellant-based solutions or suspensions used in metered dose        inhaler or even specially engineered powder mixtures for the dry        powder inhalers. All these different formulations require        different principles for aerosol generation, which emphasizes        the mutual dependency of device and formulation;    -   Since the site of deposition of aerosol particles depends on        their (aerodynamic) size and velocity, the desired particle size        of the aerosol cloud varies depending on the desired site of        deposition in the lung, which is related to the therapeutic goal        of the administration;    -   As the aerosol cloud can be tuned to be released at different        moments during the inhalation cycle generated by the mammal, it        is preferred that for the agents of the invention (to be        deposited in the peripheral parts of the lung) the aerosol is        released at the start of the inhalation cycle;    -   Doses may vary considerably and may e.g. vary e.g. for a human        from a few microgram to several hundreds of microgram or even        milligrams, e.g. about up to about 10 to 100 milligrams.

Various inhalation systems are e.g. described on pages 129 to 148 in thereview (“Pulmonary Drug Delivery”, Bechtold-Peters and Luessen, eds.,supra) and include, but are not limited to, nebulizers, metered doseinhalers, metered dose liquid inhalers, and dry powder inhalers. Devicestaking into account optimized and individualized breathing pattern forcontrolled inhalation maneuvers may also be used (see AKITA® technologyon page 157 of “Pulmonary Drug Delivery”, Bechtold-Peters and Luessen,eds., supra).

However, not only the device is important to pulmonary delivery of theamino acid sequences, Nanobodies®, compounds, constructs and/orpolypeptides of the invention but also the right formulation is criticalto achieve an effective delivery. This can be in principle achieved byusing one of the following approaches:

-   -   Administration of aqueous solutions or suspensions comprising        the amino acid sequences, Nanobodies®, compounds, constructs        and/or polypeptides of the invention (e.g. nasal drops) into the        nasal cavities;    -   Nebulisation of aqueous solutions or suspensions comprising the        amino acid sequences, Nanobodies®, compounds, constructs and/or        polypeptides of the invention;    -   Atomization by means of liquefied propellants; and    -   Dispersion of dry powders.

Hence formulations of the amino acid sequences, Nanobodies®, compounds,constructs and/or polypeptides of the invention have to be adopted andadjusted to the chosen inhalation device. Appropriate formulations, i.e.the excipients in addition to the amino acid sequences, Nanobodies®,compounds, constructs and/or polypeptides of the invention, are e.g.described in chapter IV of “Pulmonary Drug Delivery”, Bechtold-Petersand Luessen, eds., supra. In this respect, reference is also made toU.S. provisional application No. 61/303,447 entitled “Methods andcompositions for the preparation of aerosols” filed by Ablynx N. V. on12 Feb. 2010.

The amount of the amino acid sequences, Nanobodies®, compounds,constructs and polypeptides of the invention required for use intreatment will vary not only with the particular amino acid sequence,Nanobody®, compounds, constructs or polypeptide selected but also withthe route of administration, the nature of the condition being treatedand the age and condition of the patient and will be ultimately at thediscretion of the attendant physician or clinician. Also the dosage ofthe amino acid sequences, Nanobodies®, compounds, constructs andpolypeptides of the invention varies depending on the target host cell,tumor, tissue, graft, or organ.

The desired dose may conveniently be presented in a single dose or asdivided doses administered at appropriate intervals, for example, astwo, three, four or more sub-doses per day. The sub-dose itself may befurther divided, e.g., into a number of discrete loosely spacedadministrations; such as multiple inhalations from an insufflator or byapplication of a plurality of drops into the eye.

An administration regimen could include long-term, daily treatment. By“long-term” is meant at least two weeks and preferably, several weeks,months, or years of duration. Necessary modifications in this dosagerange may be determined by one of ordinary skill in the art using onlyroutine experimentation given the teachings herein. See Remington'sPharmaceutical Sciences (Martin, E. W., ed. 4), Mack Publishing Co.,Easton, Pa. The dosage can also be adjusted by the individual physicianin the event of any complication.

The invention further relates to applications and uses of the amino acidsequences, Nanobodies®, polypeptides, compounds, nucleic acids, hostcells, products and compositions described herein, as well as to methodsfor the prevention and/or treatment respiratory track infection causedby hRSV. Some preferred but non-limiting applications and uses willbecome clear from the further description herein.

The amino acid sequences, Nanobodies®, polypeptides, compounds andcompositions of the present invention can generally be used to block theinteraction of protein F of hRSV with the target host cell and/or itsmembrane, to neutralize hRSV (different hRSV strains and/or escapemutants), to modulate, inhibit and/or prevent hRSV infectivity (ofdifferent hRSV strains and/or escape mutants), to modulate, inhibitand/or prevent fusion (of different hRSV strains and/or escape mutants)with (the cell membrane of) the target host cell and/or to modulate,inhibit and/or prevent hRSV entry in the target host cell (of differenthRSV strains and/or escape mutants).

In one aspect, the amino acid sequences, Nanobodies®, polypeptides,compounds and compositions of the present invention can block theinteraction of protein F of hRSV with the target host cell and/or itsmembrane by at least 1%, preferably at least 5%, such as at least 10% orat least 25%, for example by at least 50%, at least 60%, at least 70%,at least 80%, or 90% or more, compared to the interaction of protein Fof hRSV with the target host cell and/or its membrane under the sameconditions but without the presence of the amino acid sequence,Nanobody® or polypeptide of the invention, measured in any suitablemanner known per se, for example using one of the assays describedherein.

In another aspect, the amino acid sequences, Nanobodies®, polypeptides,compounds and compositions of the present invention neutralize hRSVinfectivity by at least 1%, preferably at least 5%, such as at least 10%or at least 25%, for example by at least 50%, at least 60%, at least70%, at least 80%, or 90% or more, compared to, the neutralization ofhRSV under the same conditions but without the presence of the aminoacid sequence, Nanobody® or polypeptide of the invention, measured inany suitable manner known per se, for example using one of the assaysdescribed herein.

In the context of the present invention, “modulating” or “to modulate”generally means either reducing, preventing or inhibiting viralinfectivity, fusion and/or viral entry and/or reducing, preventing orinhibiting the biological pathways that are mediated by protein F ofhRSV, as measured using a suitable in vitro, cellular or in vivo assay(such as those mentioned herein). In particular, “modulating” or “tomodulate” may mean either reducing, preventing or inhibiting viralinfectivity, fusion and/or viral entry and/or reducing, preventing orinhibiting the biological pathways that are mediated by protein F ofhRSV as measured using a suitable in vitro, cellular or in vivo assay(such as those mentioned herein), by at least 1%, preferably at least5%, such as at least 10% or at least 25%, for example by at least 50%,at least 60%, at least 70%, at least 80%, or 90% or more, compared tonormal (i.e. naturally occurring) viral infectivity, fusion and/or viralentry and/or normal (i.e. naturally occurring) the biological pathwaysthat are mediated by protein F of hRSV in the same assay under the sameconditions but without the presence of the amino acid sequence,Nanobody® or polypeptide of the invention.

In one aspect, the amino acid sequences, Nanobodies®, polypeptides,compounds and compositions of the present invention may modulate,inhibit and/or prevent hRSV infectivity by at least 1%, preferably atleast 5%, such as at least 10% or at least 25%, for example by at least50%, at least 60%, at least 70%, at least 80%, or 90% or more, comparedto the infectivity under the same conditions but without the presence ofthe amino acid sequence, Nanobody® or polypeptide of the invention,measured in any suitable manner known per se, for example using one ofthe assays described herein.

The term “viral entry” used herein encompasses any viral-mediatedbiological pathway that is needed to accomplish virion attachment to atarget host cell and/or viral fusion with a target host cell. It isencompassed in the present invention that viral entry, which may be anyviral-mediated biological pathway that is needed to accomplish virionattachment to a target host cell and/or viral fusion with a target hostcell, can be modulated and/or reduced and/or prevented and/or inhibitedby specific binding of the amino acid sequences, Nanobodies®,polypeptides and/or compounds of the invention, as measured using asuitable in vitro, cellular or in vivo assay (such as those mentionedherein). In particular, viral entry, which can be mediated by protein Fof hRSV, can be modulated, reduced, prevented or inhibited by specificbinding of the amino acid sequences, Nanobodies®, polypeptides and/orcompounds of the invention to protein F of hRSV, as measured using asuitable in vitro, cellular or in vivo assay (such as those mentionedherein), by at least 1%, preferably at least 5%, such as at least 10% orat least 25%, for example by at least 50%, at least 60%, at least 70%,at least 80%, or 90% or more, compared to normal (i.e. naturallyoccurring) viral entry (as defined herein), which can be mediated byprotein F of hRSV, in the same assay under the same conditions butwithout the presence of the amino acid sequence, Nanobody®, polypeptideand/or compound of the invention. Thus, it is also encompassed that thatviral attachment and/or viral fusion can be modulated and/or reducedand/or prevented and/or inhibited by specific binding of the amino acidsequences, Nanobodies®, polypeptides and/or compounds of the inventionto protein F of hRSV, as measured using a suitable in vitro, cellular orin vivo assay (such as those mentioned herein). In particular, viralattachment and/or viral fusion, which can be mediated by protein F ofhRSV, can be modulated, reduced, prevented or inhibited by specificbinding of the amino acid sequences, Nanobodies®, polypeptides and/orcompounds of the invention to protein F of hRSV, as measured using asuitable in vitro, cellular or in vivo assay (such as those mentionedherein), by at least 1%, preferably at least 5%, such as at least 10% orat least 25%, for example by at least 50%, at least 60%, at least 70%,at least 80%, or 90% or more, compared to normal (i.e. naturallyoccurring) viral attachment and/or viral fusion, which can be mediatedby protein F of hRSV in the same assay under the same conditions butwithout the presence of the amino acid sequence, Nanobody®, polypeptideand/or compound of the invention.

In this respect, the amino acid sequences, Nanobodies®, polypeptides,compounds and compositions of the present invention may modulate,inhibit and/or prevent hRSV entry in the target host cell by at least1%, preferably at least 5%, such as at least 10% or at least 25%, forexample by at least 50%, at least 60%, at least 70%, at least 80%, or90% or more, compared to the entry in the target host cell under thesame conditions but without the presence of the amino acid sequence,Nanobody® or polypeptide of the invention, for example using one of theassays described herein.

The amino acid sequences, Nanobodies®, polypeptides, compounds andcompositions of the present invention may also modulate, inhibit and/orprevent fusion of hRSV with (the cell membrane of) the target host cellby at least 1%, preferably at least 5%, such as at least 10% or at least25%, for example by at least 50%, at least 60%, at least 70%, at least80%, or 90% or more, compared to fusion of hRSV with (the cell membraneof) the target host cell under the same conditions but without thepresence of the amino acid sequence, Nanobody® or polypeptide of theinvention, measured in any suitable manner known per se, for exampleusing one of the assays described herein.

The multivalent (such as bivalent or trivalent) polypeptides of theinvention have shown improved affinity and/or improved cross-reactivityfor different genotypes, subtypes, viral escape mutants and/or strainsof hRSV compared to the monovalent amino acid sequence or Nanobody®. Inone aspect, the multivalent (such as bivalent or trivalent) polypeptidesof the invention may bind different strains of RSV (such as e.g. Long,A-2 and/or B-1). In yet another aspect, the multivalent (such asbivalent or trivalent) polypeptides of the invention may bind differentescape mutants of hRSV (such as e.g. described in Lopez et al. 1998, J.Virol. 72: 6922-6928) and/or escape mutants specific for antigen siteII, antigen site IV-VI or the combination of both antigenic sites.

Accordingly, the invention also relates to the use of a multivalent(e.g. trivalent, bivalent) polypeptide of the invention, and/or of apharmaceutical composition comprising the same for binding and/orneutralization of different strains of a hRSV. In a preferred aspect, abivalent humanized and/or sequence optimized NC41 Nanobody® (such ase.g. a bivalent polypeptide comprising two Nanobodies® selected from SEQID NO's: 60-76, 138-141 and 146-157) is used. In another preferredaspect, a trivalent humanized and/or sequence optimized NC41 Nanobody®(such as e.g. a trivalent polypeptide comprising three Nanobodies®selected from SEQ ID NO's: 60-76, 138-141 and 146-157) is used. Inanother preferred aspect, one of SEQ ID NO's: 77-79, 142-145 and 158-165is used.

The invention also relates to the use of a multivalent (e.g. trivalent,bivalent) polypeptide of the invention, and/or of a pharmaceuticalcomposition comprising the same for binding and/or neutralization of oneor more escape mutants of a hRSV. In a preferred aspect, a bivalenthumanized NC41 Nanobody® (such as e.g. a bivalent polypeptide comprisingtwo Nanobodies® selected from SEQ ID NO's: 60-76, 138-141 and 146-157)is used. In another preferred aspect, a trivalent humanized NC41Nanobody® (such as e.g. a trivalent polypeptide comprising threeNanobodies® selected from SEQ ID NO's: 60-76, 138-141 and 146-157) isused. In another preferred aspect, one of SEQ ID NO's: 77-79, 142-145and 158-165 is used.

The invention also relates to a method for the prevention and/ortreatment of at least one viral disease, said method comprisingadministering, to a subject in need thereof, a pharmaceutically activeamount of an amino acid sequence of the invention, of a Nanobody® of theinvention, of a polypeptide of the invention, of a compound or constructof the invention and/or of a pharmaceutical composition comprising thesame.

As such, the amino acid sequences, Nanobodies®, polypeptides, compoundsand compositions of the present invention can be used for the preventionand/or treatment of diseases and disorders associated with hRSVinfection. Examples of such diseases and disorders associated with hRSVinfection will be clear to the skilled person based on the disclosureherein, and for example include the following diseases and disorders:respiratory illness, upper respiratory tract infection, lowerrespiratory tract infection, bronchiolitis (inflammation of the smallairways in the lung), pneumonia, dyspnea, cough, (recurrent) wheezingand asthma.

Accordingly, the present invention also relates to a method for theprevention and/or treatment of respiratory illness, upper respiratorytract infection, lower respiratory tract infection, bronchiolitis(inflammation of the small airways in the lung), pneumonia, dyspnea,cough, (recurrent) wheezing and/or asthma caused by hRSV, said methodcomprising administering, to a subject in need thereof, apharmaceutically active amount of at least one amino acid sequence ofthe invention, Nanobody® of the invention, polypeptide of the invention,compound or construct of the invention or monovalent construct of theinvention, or a composition of the invention.

The invention also relates to the use of an amino acid sequence of theinvention, a Nanobody® of the invention, a polypeptide of the invention,a compound or construct of the invention or monovalent construct of theinvention in the preparation of a pharmaceutical composition forprevention and/or treatment of respiratory illness, upper respiratorytract infection, lower respiratory tract infection, bronchiolitis(inflammation of the small airways in the lung), pneumonia, dyspnea,cough, (recurrent) wheezing and/or asthma; and/or for use in one or moreof the methods described herein.

The invention also relates to an amino acid sequence of the invention, aNanobody® of the invention, a polypeptide of the invention, a compoundor construct of the invention or monovalent construct of the inventionfor prevention and/or treatment of respiratory illness, upperrespiratory tract infection, lower respiratory tract infection,bronchiolitis (inflammation of the small airways in the lung),pneumonia, dyspnea, cough, (recurrent) wheezing and/or asthma.

In the context of the present invention, the term “prevention and/ortreatment” not only comprises preventing and/or treating the disease,but also generally comprises preventing the onset of the disease,slowing or reversing the progress of disease, preventing or slowing theonset of one or more symptoms associated with the disease, reducingand/or alleviating one or more symptoms associated with the disease,reducing the severity and/or the duration of the disease and/or of anysymptoms associated therewith and/or preventing a further increase inthe severity of the disease and/or of any symptoms associated therewith,preventing, reducing or reversing any physiological damage caused by thedisease, and generally any pharmacological action that is beneficial tothe patient being treated.

The subject to be treated may be any warm-blooded animal, but is inparticular a mammal, and more in particular a human being. As will beclear to the skilled person, the subject to be treated will inparticular be a person suffering from, or at risk of, the diseases anddisorders mentioned herein.

More in particular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV, said method comprisingadministering, to a subject in need thereof, a pharmaceutically activeamount of a multivalent (e.g. trivalent or bivalent) polypeptide orcompound of the invention, and/or of a pharmaceutical compositioncomprising the same. More in particular, the present invention mayrelate to a method for the prevention and/or treatment of infection byhRSV, said method comprising administering, to a subject in needthereof, a pharmaceutically active amount of a bivalent compound orpolypeptide of the invention. More in particular, the present inventionmay relate to a method for the prevention and/or treatment of infectionby hRSV, said method comprising administering, to a subject in needthereof, a pharmaceutically active amount of a bivalent humanized and/orsequence optimized NC41 Nanobody® (such as e.g. a bivalent polypeptidecomprising two Nanobodies® selected from SEQ ID NO's: 60-76, 138-141 and146-157). More in particular, the present invention may relate to amethod for the prevention and/or treatment of infection by hRSV, saidmethod comprising administering, to a subject in need thereof, apharmaceutically active amount of a trivalent compound or polypeptide ofthe invention. More in particular, the present invention may relate to amethod for the prevention and/or treatment of infection by hRSV, saidmethod comprising administering, to a subject in need thereof, apharmaceutically active amount of a trivalent humanized NC41 Nanobody®(such as e.g. a trivalent polypeptide comprising three Nanobodies®selected from SEQ ID NO's: 60-76, 138-141 and 146-157). More inparticular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV, said method comprisingadministering, to a subject in need thereof, a pharmaceutically activeamount of one of SEQ ID NO's: 77-79, 142-145 and 158-165.

More in particular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV said method comprisingadministering to the pulmonary tissue of a subject in need thereof, apharmaceutically active amount of an amino acid sequence of theinvention, of a Nanobody® of the invention, of a polypeptide of theinvention, and/or of a pharmaceutical composition comprising the same.

In another aspect, the invention relates to a method for immunotherapy,and in particular for passive immunotherapy, which method comprisesadministering, to a subject suffering from or at risk of the diseasesand disorders mentioned herein, a pharmaceutically active amount of anamino acid sequence of the invention, of a Nanobody® of the invention,of a polypeptide of the invention, of a compound or construct of theinvention and/or of a pharmaceutical composition comprising the same.

In the above methods, the amino acid sequences, Nanobodies®, compoundsor constructs and/or polypeptides of the invention and/or thecompositions comprising the same can be administered in any suitablemanner, depending on the specific pharmaceutical formulation orcomposition to be used. Thus, the amino acid sequences, Nanobodies®and/or polypeptides of the invention and/or the compositions comprisingthe same can for example be administered orally, intraperitoneally (e.g.intravenously, subcutaneously, intramuscularly, or via any other routeof administration that circumvents the gastrointestinal tract),intranasally, transdermally, topically, by means of a suppository, byinhalation, again depending on the specific pharmaceutical formulationor composition to be used. The clinician will be able to select asuitable route of administration and a suitable pharmaceuticalformulation or composition to be used in such administration, dependingon the disease or disorder to be prevented or treated and other factorswell known to the clinician.

Thus, in general, the amino acid sequences, Nanobodies®, compounds orconstructs and polypeptides according to the invention and/or thecompositions comprising the same can be administered in any suitablemanner; for example but not limited thereto, the amino acid sequences,Nanobodies®, compounds or constructs and polypeptides according to theinvention and compositions comprising the same can be administeredintranasally and/or by inhalation and/or by any other suitable form ofpulmonary delivery; methods for pulmonary delivery and/or intranasaldelivery and/or delivery by inhalation of a Nanobody®, amino acidsequence, compound or construct and/or polypeptide of the invention willbe known to the skilled person and are e.g. described in the handbook“Drug Delivery: Principles and Applications” (2005) by Binghe Wang,Teruna Siahaan and Richard Soltero (Eds, Wiley Interscience (John Wiley& Sons)); in the International application WO 08/049,897 of Ablynx N. V.entitled “Intranasal delivery of polypeptides and proteins”; in“Pharmacology PreTest™ Self-Assessment and Review” (11^(th) Edition) byRosenfeld G. C., Loose-Mitchell D. S.; and in “Pharmacology” (3^(rd)Edition) by Lippincott Williams & Wilkins, New York; Shlafer M.McGraw-Hill Medical Publishing Division, New York; Yang K. Y., Graff L.R., Caughey A. B. Blueprints Pharmacology, Blackwell Publishing.

Accordingly, the present invention also relates to a method foradministering an effective amount of a amino acid sequence, Nanobody®,compound or construct and/or polypeptide of the invention and/or acomposition comprising the same, wherein said method comprises the stepof administering the amino acid sequence, Nanobody®, compound orconstruct and/or polypeptide and/or composition comprising the same tothe pulmonary tissue. In such method, the amino acid sequence,Nanobody®, compound or construct and/or polypeptide and/or a compositioncomprising the same can be administered by any method know in the artfor pulmonary delivery such as e.g. by use of an inhaler or intranasaldelivery device or aerosol.

In a preferred aspect of the invention, the amino acid sequence,Nanobody®, compound or construct and/or polypeptide will bind and/orneutralize virus present in the pulmonary tissue. Preferably in suchmethod for pulmonary delivery at least 5%, preferably at least 10%, 20%,30%, 40%, more preferably at least 50%, 60%, 70%, and even morepreferably at least 80% or more of the amino acid sequence, Nanobody®,compound or construct and/or polypeptide of the invention is stable inthe pulmonary tissue for at least 24 hours, preferably at least 48 hoursmore preferably at least 72 hours.

It has been surprisingly found that the amino acid sequences,Nanobodies®, compounds or constructs and/or polypeptides of theinvention have a long lasting stability in the pulmonary tissue. E.g. ithas been found that a Nanobody® directed against hRSV remains functionalin the lung for at least 48 hours (see PCT/EP2009/056975 entitled Aminoacid sequences directed against envelope proteins of a virus andpolypeptides comprising the same for the treatment of viral diseasesfiled by Ablynx N. V. on 5 Jun. 2009). Thus, embodiments of theinvention with treatment intervals such as once a day, once every2^(nd), 3^(rd), 4^(th), 5^(th), 6^(th) or once every week are thought tobe possible taken the estimated long lasting stability of the amino acidsequences, Nanobodies®, compounds or constructs and/or polypeptides ofthe invention.

Accordingly, the invention relates to a method for delivering an aminoacid sequence, Nanobody®, compound or construct and/or polypeptide ofthe invention to the pulmonary tissue of a subject without beinginactivated, said method comprising the step of pulmonary administeringsaid amino acid sequence, Nanobody®, compound or construct and/orpolypeptide of the invention to said subject.

The invention also relates to a method for the prevention and/ortreatment of hRSV infection, said method comprising administering to thepulmonary tissue of a subject in need thereof, a pharmaceutically activeamount of an amino acid sequence of the invention, of a Nanobody® of theinvention, of a polypeptide of the invention, of a compound or constructof the invention and/or of a pharmaceutical composition comprising thesame.

More in particular, the invention relates to a method for the preventionand/or treatment of respiratory illness, upper respiratory tractinfection, lower respiratory tract infection, bronchiolitis(inflammation of the small airways in the lung), pneumonia, dyspnea,cough, (recurrent) wheezing and/or asthma, said method comprisingadministering, to the pulmonary tissue of a subject in need thereof, apharmaceutically active amount of an amino acid sequence of theinvention, of a Nanobody® of the invention, of a polypeptide of theinvention, of a compound or construct of the invention and/or of apharmaceutical composition comprising the same.

More in particular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV, said method comprisingadministering, to the pulmonary tissue of a subject in need thereof, apharmaceutically active amount of a multivalent (e.g. trivalent,bivalent) polypeptide or compound of the invention, and/or of apharmaceutical composition comprising the same. More in particular, thepresent invention may relate to a method for the prevention and/ortreatment of infection by hRSV, said method comprising administering, tothe pulmonary tissue of a subject in need thereof, a pharmaceuticallyactive amount of a bivalent compound or polypeptide of the invention.More in particular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV, said method comprisingadministering, to the pulmonary tissue of a subject in need thereof, apharmaceutically active amount of a bivalent humanized NC41 Nanobody®(such as e.g. a bivalent polypeptide comprising two Nanobodies® selectedfrom SEQ ID NO's: 60-76, 138-141 and 146-157). More in particular, thepresent invention may relate to a method for the prevention and/ortreatment of infection by hRSV, said method comprising administering, tothe pulmonary tissue of a subject in need thereof, a pharmaceuticallyactive amount of a trivalent compound or polypeptide of the invention.More in particular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV, said method comprisingadministering, to the pulmonary tissue of a subject in need thereof, apharmaceutically active amount of a trivalent humanized NC41 Nanobody®(such as e.g. a trivalent polypeptide comprising three Nanobodies®selected from SEQ ID NO's: 60-76, 138-141 and 146-157). More inparticular, the present invention may relate to a method for theprevention and/or treatment of infection by hRSV, said method comprisingadministering, to the pulmonary tissue of a subject in need thereof, apharmaceutically active amount of one of SEQ ID NO's: 77-79, 142-145 and158-165.

Also for example but not limited thereto, the amino acid sequences,Nanobodies®, compounds or constructs, and polypeptides according to theinvention and compositions comprising the same, can be administeredintramuscularly and/or by any suitable form of delivery to the brain,such as any suitable form of delivery which allows said amino acidsequences, Nanobodies®, polypeptides, compounds or constructs andcompositions comprising the same to be transported across theblood-brain-barrier. Such methods for intramuscular delivery and/or anysuitable form of delivery to the brain of a Nanobody®, amino acidsequence and/or polypeptide of the invention will be known to theskilled person and are e.g. described in the handbook “Drug Delivery:Principles and Applications” (2005) by Binghe Wang, Teruna Siahaan andRichard Soltero (Eds. Wiley Interscience (John Wiley & Sons)); in“Pharmacology PreTest™ Self-Assessment and Review” (11^(th) Edition) byRosenfeld G. C., Loose-Mitchell D. S.; and in “Pharmacology” (3^(rd)Edition) by Lippincott Williams & Wilkins, New York; Shlafer M.McGraw-Hill Medical Publishing Division, New York; Yang K. Y., Graff L.R., Caughey A. B. Blueprints Pharmacology, Blackwell Publishing.

The amino acid sequences, Nanobodies®, compounds or constructs and/orpolypeptides of the invention and/or the compositions comprising thesame are administered according to a regime of treatment that issuitable for preventing and/or treating the disease or disorder to beprevented or treated. The clinician will generally be able to determinea suitable treatment regimen, depending on factors such as the diseaseor disorder to be prevented or treated, the severity of the disease tobe treated and/or the severity of the symptoms thereof, the specificamino acid sequence, Nanobody®, compound or construct or polypeptide ofthe invention to be used, the specific route of administration andpharmaceutical formulation or composition to be used, the age, gender,weight, diet, general condition of the patient, and similar factors wellknown to the clinician.

Generally, the treatment regimen will comprise the administration of oneor more amino acid sequences, Nanobodies®, compounds or constructsand/or polypeptides of the invention, or of one or more compositionscomprising the same, in one or more pharmaceutically effective amountsor doses. The specific amount(s) or doses to administered can bedetermined by the clinician, again based on the factors cited above.

Generally, for the prevention and/or treatment of the diseases anddisorders mentioned herein and depending on the specific disease ordisorder to be treated, the potency of the specific amino acid sequence,Nanobody®, compound or construct and polypeptide of the invention to beused, the specific route of administration and the specificpharmaceutical formulation or composition used, the amino acidsequences, Nanobodies®, compounds or constructs and polypeptides of theinvention will generally be administered in an amount between 1 gram and1 microgram per kg body weight per day, preferably between 0.1 gram and10 microgram per kg body weight per day, most preferably between 0.01gram and 100 microgram per kg body weight per day such as about 0.1,0.5, 1, 2, 5 or 10 milligram per kg body weight per day, eithercontinuously (e.g. by infusion), as a single daily dose or as multipledivided doses during the day. Amino acid sequences, Nanobodies®,compounds or constructs and polypeptides of the invention that contain ahalf-life extending moiety may be administered in an amount between 1milligram and 100 milligram per kg body weight, preferably between 1milligram and 50 milligram per kg body weight, such as about 10, 15, 20or 30 milligram per kg body weight once or twice a month. The clinicianwill generally be able to determine a suitable daily dose, depending onthe factors mentioned herein. It will also be clear that in specificcases, the clinician may choose to deviate from these amounts, forexample on the basis of the factors cited above and his expert judgment.Generally, some guidance on the amounts to be administered can beobtained from the amounts usually administered for comparableconventional antibodies or antibody fragments against the same targetadministered via essentially the same route, taking into account howeverdifferences in affinity/avidity, efficacy, biodistribution, and similarfactors well known to the skilled person.

When the amino acid sequence, Nanobody®, compound or construct and/orpolypeptide and/or a composition comprising the same is administered tothe pulmonary tissue the treatment regime may be once or twice daily,preferably once daily, or once every 2, 3, 4, 5, 6, or 7 days.

Usually, in the above method, a single amino acid sequence, Nanobody®,compound or construct, or polypeptide of the invention will be used. Itis however within the scope of the invention to use two or more aminoacid sequences, Nanobodies®, compounds or constructs and/or polypeptidesof the invention in combination.

The Nanobodies®, amino acid sequences, compounds or constructs andpolypeptides of the invention may also be used in combination with oneor more further pharmaceutically active compounds or principles, i.e. asa combined treatment regimen, which may or may not lead to a synergisticeffect. Again, the clinician will be able to select such furthercompounds or principles, as well as a suitable combined treatmentregimen, based on the factors cited above and his expert judgement.

In particular, the amino acid sequences, Nanobodies®, compounds orconstructs, and polypeptides of the invention may be used in combinationwith other pharmaceutically active compounds or principles that are orcan be used for the prevention and/or treatment of the diseases anddisorders cited herein, as a result of which a synergistic effect may ormay not be obtained. Examples of such compounds and principles, as wellas routes, methods and pharmaceutical formulations or compositions foradministering them will be clear to the clinician.

When two or more substances or principles are to be used as part of acombined treatment regimen, they can be administered via the same routeof administration or via different routes of administration, atessentially the same time or at different times (e.g. essentiallysimultaneously, consecutively, or according to an alternating regime).When the substances or principles are to be administered simultaneouslyvia the same route of administration, they may be administered asdifferent pharmaceutical formulations or compositions or part of acombined pharmaceutical formulation or composition, as will be clear tothe skilled person.

Also, when two or more active substances or principles are to be used aspart of a combined treatment regimen, each of the substances orprinciples may be administered in the same amount and according to thesame regimen as used when the compound or principle is used on its own,and such combined use may or may not lead to a synergistic effect.However, when the combined use of the two or more active substances orprinciples leads to a synergistic effect, it may also be possible toreduce the amount of one, more or all of the substances or principles tobe administered, while still achieving the desired therapeutic action.This may for example be useful for avoiding, limiting or reducing anyunwanted side-effects that are associated with the use of one or more ofthe substances or principles when they are used in their usual amounts,while still obtaining the desired pharmaceutical or therapeutic effect.

The effectiveness of the treatment regimen used according to theinvention may be determined and/or followed in any manner known per sefor the disease or disorder involved, as will be clear to the clinician.The clinician will also be able, where appropriate and on a case-by-casebasis, to change or modify a particular treatment regimen, so as toachieve the desired therapeutic effect, to avoid, limit or reduceunwanted side-effects, and/or to achieve an appropriate balance betweenachieving the desired therapeutic effect on the one hand and avoiding,limiting or reducing undesired side effects on the other hand.

Generally, the treatment regimen will be followed until the desiredtherapeutic effect is achieved and/or for as long as the desiredtherapeutic effect is to be maintained. Again, this can be determined bythe clinician.

In another aspect, the invention relates to the use of an amino acidsequence, Nanobody®, compound or construct, or polypeptide of theinvention in the preparation of a pharmaceutical composition forprevention and/or treatment of at least one viral disease; and/or foruse in one or more of the methods of treatment mentioned herein.

The subject to be treated may be any warm-blooded animal, but is inparticular a mammal, and more in particular a human being. As will beclear to the skilled person, the subject to be treated will inparticular be a person suffering from, or at risk of, the diseases anddisorders mentioned herein.

The invention also relates to the use of an amino acid sequence,Nanobody®, compound or construct or polypeptide of the invention in thepreparation of a pharmaceutical composition for the prevention and/ortreatment of at least one disease or disorder that can be preventedand/or treated by administering an amino acid sequence, Nanobody®,compound or construct or polypeptide of the invention to a patient.

More in particular, the invention relates to the use of an amino acidsequence, Nanobody®, compound or construct or polypeptide of theinvention in the preparation of a pharmaceutical composition for theprevention and/or treatment of viral diseases, and in particular for theprevention and treatment of one or more of the diseases and disorderslisted herein.

Again, in such a pharmaceutical composition, the one or more amino acidsequences, Nanobodies®, compounds or constructs or polypeptides of theinvention may also be suitably combined with one or more other activeprinciples, such as those mentioned herein.

Further uses of the amino acid sequences, Nanobodies®, polypeptides,nucleic acids, genetic constructs and hosts and host cells of theinvention will be clear to the skilled person based on the disclosureherein. For example, and without limitation, the amino acid sequences ofthe invention can be linked to a suitable carrier or solid support so asto provide a medium than can be used in a manner known per se to purifyan envelope protein of a virus from compositions and preparationscomprising the same. Derivatives of the amino acid sequences of theinvention that comprise a suitable detectable label can also be used asmarkers to determine (qualitatively or quantitatively) the presence ofan envelope protein of a virus in a composition or preparation or as amarker to selectively detect the presence of an envelope protein of avirus on the surface of a cell or tissue (for example, in combinationwith suitable cell sorting techniques).

The invention will now be further described by means of the followingnon-limiting preferred aspects, examples and figures:

The entire contents of all of the references (including literaturereferences, issued patents, published patent applications, andco-pending patent applications) cited throughout this application arehereby expressly incorporated by reference, in particular for theteaching that is referenced hereinabove.

Aspects

-   Aspect A-1. Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV and that comprises at least a    stretch of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.-   Aspect A-2. Amino acid sequence according to aspect A-1, that    comprises two or more stretches of amino acid residues in which one    stretch is chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a) and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).-   Aspect A-3. Amino acid sequence according to aspect A-1 or A-2, that    comprises three or more stretches of amino acid residues, in which    the first stretch of amino acid residues is chosen from the group    consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   the second stretch of amino acid residues is chosen from the        group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and the third stretch of amino acid residues is chosen from the        group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.-   Aspect A-4. Amino acid sequence according to any of aspects A-1 to    A-3, that specifically binds antigenic site II on protein F of hRSV    and/or that competes with Synagis® for binding protein F of hRSV.-   Aspect A-5, Amino acid sequence according to any of aspects A-1 to    A-4, that is a naturally occurring amino acid sequence (from any    suitable species) or a synthetic or semi-synthetic amino acid    sequence.-   Aspect A-6. Amino acid sequence according to any of aspects A-1 to    A-5, that comprises an immunoglobulin fold or that under suitable    conditions is capable of forming an immunoglobulin fold.-   Aspect A-7. Amino acid sequence according to any of aspects A-1 to    A-6, that is an immunoglobulin sequence.-   Aspect A-8. Amino acid sequence according to any of aspects A-1 to    A-7, that is a naturally occurring immunoglobulin sequence (from any    suitable species) or a synthetic or semi-synthetic immunoglobulin    sequence.-   Aspect A-9. Amino acid sequence according to any of aspects A-1 to    A-8, that is a humanized immunoglobulin sequence, a camelized    immunoglobulin sequence or an immunoglobulin sequence that has been    obtained by techniques such as affinity maturation.-   Aspect A-10. Amino acid sequence according to any of aspects A-1 to    A-9, that essentially consists of a heavy chain variable domain    sequence (e.g. a V_(H)-sequence).-   Aspect A-11. Amino acid sequence according to any of aspects A-1 to    A-10, that essentially consists of a heavy chain variable domain    sequence that is derived from a conventional four-chain antibody or    that essentially consist of a heavy chain variable domain sequence    that is derived from heavy chain antibody.-   Aspect A-12. Amino acid sequence according to any of aspects A-1 to    A-11, that essentially consists of a domain antibody (or an amino    acid sequence that is suitable for use as a domain antibody), of a    single domain antibody (or an amino acid sequence that is suitable    for use as a single domain antibody), of a “dAb” (or an amino acid    sequence that is suitable for use as a dAb) or of a Nanobody®    (including but not limited to a V_(H), sequence).-   Aspect A-13. Amino acid sequence according to any of aspects A-1 to    A-12, that essentially consist of 4 framework regions (FR1 to FR4,    respectively) and 3 complementarity determining regions (CDR1 to    CDR3, respectively), in which CDR2 is chosen from:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.-   Aspect A-14. Amino acid sequence according to aspect A-13, that    essentially consists of 4 framework regions (FR1 to FR4,    respectively) and 3 complementarity determining regions (CDR1 to    CDR3, respectively), in which CDR2 is chosen from the group    consisting of:    -   a) SEQ ID NO: 102; or    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one of CDR1 or CDR3 is chosen from:        -   CDR1 chosen from the group consisting of:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and/or        -   CDR3 chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.-   Aspect A-15. Amino acid sequence according to any of aspects A-13 or    A-14, that consists of 4 framework regions (FR1 to FR4,    respectively) and 3 complementarity determining regions (CDR1 to    CDR3, respectively), in which:    -   CDR1 is chosen from the group consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and        -   CDR2 is chosen from the group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and        -   CDR3 is chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.-   Aspect A-16. Amino acid sequence according to any of aspects A-1 to    A-15, that comprises at least SEQ ID NO: 102.-   Aspect A-17. Amino acid sequence according to aspect A-16, that    comprises at least SEQ ID NO: 102 and at least one stretch of amino    acid residues (CDR sequence) chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.-   Aspect A-18, Amino acid sequence according to any of aspects A-16 or    A-17, that comprises at least SEQ ID NO: 102 and a CDR1 sequence    chosen from:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and a CDR3 sequence chosen from:    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.-   Aspect A-19. Amino acid sequence according to any of aspects A-16 to    A-18, that comprises at least SEQ ID NO: 102 and at least one    stretch of amino acid residues (CDR sequence) chosen from SEQ ID NO:    98 and SEQ ID NO: 121.-   Aspect A-20. Amino acid sequence according to any of aspects A-16 to    A-19, that comprises SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO:    121.-   Aspect A-21. Amino acid sequence according to any of aspects A-1 to    A-20, that essentially consists of a Nanobody® that:

a) has at least 80% amino acid identity with at least one of the aminoacid sequences of SEQ ID NO's: 60-76, 138-141 and 146457, in which forthe purposes of determining the degree of amino acid identity, the aminoacid residues that form the CDR sequences are disregarded;

-   -   and in which:    -   b) preferably one or more of the amino acid residues at        positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according        to the Kabat numbering are chosen from the Hallmark residues        mentioned in Table A-3 to Table A-8 of WO 08/020,079.

-   Aspect A-22. Amino acid sequence according to any of aspects A-1 to    A-21, that essentially consists of a humanized Nanobody®.

-   Aspect A-23. Amino acid sequence according to aspect A-22, that    essentially consists of a humanized Nanobody® which can bind (as    further defined herein) to protein F of hRSV and which:    -   i) is a humanized variant of the amino acid sequences of SEQ ID        NO: 5 (see Table A-1); and/or        -   ii) has at least 80% amino acid identity with the amino acid            sequences of SEQ ID NO: 5 (see Table A-1) and/or at least            one of the amino acid sequences of SEQ ID NO's: 60-76,            138-141 and 146-157 (see Table A-4), in which for the            purposes of determining the degree of amino acid identity,            the amino acid residues that form the CDR sequences are            disregarded;    -   and in which:    -   iii) preferably one or more of the amino acid residues at        positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according        to the Kabat numbering are chosen from the Hallmark residues        mentioned in Table A-3 to Table A-8 of WO 08/020,079.

-   Aspect A-24. Amino acid sequence according to any of aspects A-1 to    A-23, that is in essentially isolated form.

-   Aspect A-25. Amino acid sequence according to any of aspects A-1 to    A-24, for administration to a subject, wherein said amino acid    sequence does not naturally occur in said subject.

-   Aspect A-26. Amino acid sequence according to any of aspects A-1 to    A-25, that can specifically bind to protein F of hRSV with a    dissociation constant (K_(D)) of 1000 nM to 1 nM or less, preferably    100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect A-27. Amino acid sequence according to any of aspects A-1 to    A-26, that can specifically bind to protein F of hRSV with a    k_(on)-rate of between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹ preferably    between 10⁵ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or    more.

-   Aspect A-28. Amino acid sequence according to any of aspects A-1 to    A-27, that can specifically bind to protein F of hRSV with a k_(off)    rate between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a    near irreversible complex with a t_(1/2) of multiple days),    preferably between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect A-29. Amino acid sequence according to any of aspects A-1 to    A-28, that can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 100 nM and 1000 nM, preferably    between 100 nM and 500 nM, or less.

-   Aspect B-1. Nanobody® that is directed against and/or that    specifically binds protein F of hRSV, in which CDR2 is chosen from:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

-   Aspect B-2. Nanobody® according to aspect B-1, in which CDR2 is    chosen from the group consisting of:    -   a) SEQ ID NO: 102; or    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one of CDR1 or CDR3 is chosen from:        -   CDR1 chosen from the group consisting of:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and/or        -   CDR3 chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect B-3. Nanobody® according to any of aspects B-1 or B-2, in    which:    -   CDR1 is chosen from the group consisting of:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and        -   CDR2 is chosen from the group consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and        -   CDR3 is chosen from the group consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect B-4. Nanobody® according to any of aspects B-1 to B-3, that    comprises at least SEQ ID NO: 102.

-   Aspect B-5. Nanobody® according to aspect B-4, that comprises at    least SEQ ID NO: 102 and at least one CDR sequence chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect B-6, Nanobody® according to any of aspects B-4 or B-5, that    comprises at least SEQ ID NO: 102 and a CDR1 sequence chosen from:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and a CDR3 sequence chosen from:    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect B-7. Nanobody® according to any of aspects B-4 to B-6, that    comprises at least SEQ ID NO: 102 and at least one CDR sequence    chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

-   Aspect B-8. Nanobody® according to any of aspects B-4 to B-7, that    comprises SEQ ID NO: 98, SEQ ID NO: 102 and SEQ ID NO: 121.

-   Aspect B-9. Nanobody® according to any of aspects B-1 to B-8, that    is in essentially isolated form.

-   Aspect B-10. Nanobody® according to any of aspects B-1 to B-9, that    can specifically bind to protein F of hRSV with a dissociation    constant (K_(D)) of 1000 nM to 1 nM or less, preferably 100 nM to 1    nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect B-11. Nanobody® according to any of aspects B-1 to B-10, that    can specifically bind to protein F of hRSV with a k_(on)-rate of    between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹    s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect B-12. Nanobody® according to any of aspects B-1 to B-11, that    can specifically bind to protein F of hRSV with a k_(off) rate    between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days), preferably    between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect B-13. Nanobody® according to any of aspects B-1 to B-12, that    can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 100 nM and 1000 nM, preferably    between 100 nM and 500 nM, or less.

-   Aspect B-14. Nanobody® according to any of aspects B-1 to B-13, that    is a naturally occurring Nanobody® (from any suitable species) or a    synthetic or semi-synthetic Nanobody®.

-   Aspect B-15. Nanobody® according to any of aspects B-1 to B-14, that    is a V_(HH) sequence, a partially humanized V_(HH) sequence, a fully    humanized V_(HH) sequence, a camelized heavy chain variable domain    or a Nanobody® that has been obtained by techniques such as affinity    maturation.

-   Aspect B-16. Nanobody® according to any of aspects B-1 to B-15,    which is a partially humanized Nanobody®.

-   Aspect B-17. Nanobody® according to any of aspects B-1 to B-16,    which is a fully humanized Nanobody®.

-   Aspect B-18. Nanobody® according to any of aspects B-1 to B-17, that    essentially consists of a humanized Nanobody® which can bind (as    further defined herein) to protein F of hRSV and which:    -   i) is a humanized variant of the amino acid sequences of SEQ ID        NO: 5 (see Table A-1); and/or    -   ii) has at least 80% amino acid identity with the amino acid        sequences of SEQ ID NO: 5 (see Table A-1) and/or at least one of        the amino acid sequences of SEQ ID NO's: 60-76, 138-141 and        146-157 (see Table A-4), in which for the purposes of        determining the degree of amino acid identity, the amino acid        residues that form the CDR sequences are disregarded;    -   and in which:    -   iii) preferably one or more of the amino acid residues at        positions 11, 37, 44, 45, 47, 83, 84, 103, 104 and 108 according        to the Kabat numbering are chosen from the Hallmark residues        mentioned in Table A-3 to Table A-8 of WO 08/020,079.

-   Aspect C-1: Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-2: Amino acid sequence according to aspect C-1, that    comprises or essentially consists of one of SEQ ID NO's: 60-76.

-   Aspect C-3: Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-4: Amino acid sequence according to aspect C-3, that is    chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-5: Amino acid sequence according to any of aspects C-3 or    C-4, that comprises or essentially consists of one of SEQ ID NO's:    62, 65, 67, 68, 75 and 76.

-   Aspect C-6: Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino add sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino add difference.

-   Aspect C-7: Amino acid sequence according to aspect C-6, that is    chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-8: Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino add sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-9: Amino acid sequence according to aspect C-8, that    comprises or essentially consists of one of SEQ ID NO's: 146-153.

-   Aspect C-10: Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-11: Amino acid sequence according to aspect C-10, that is    chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino add sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect C-12: Amino acid sequence according to any of aspects C-10 or    C-11, that comprises or essentially consists of one of SEQ ID NO's:    146-149 and 151-153.

-   Aspect C-13: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 5, in which one or more amino acid residues    have been mutated selected from the following: Val5Leu, Ala14Pro,    Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-14: Amino acid sequence according to aspect C-13,    comprising or essentially consisting of SEQ ID NO: 5, in which two    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-15: Amino acid sequence according to aspect C-14,    comprising or essentially consisting of SEQ ID NO: 5, in which three    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-16: Amino acid sequence according to aspect C-15,    comprising or essentially consisting of SEQ ID NO: 5, in which four    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-17: Amino acid sequence according to aspect C-16,    comprising or essentially consisting of SEQ ID NO: 5, in which five    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-18: Amino acid sequence according to aspect C-17,    comprising or essentially consisting of SEQ ID NO: 5, in which six    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-19: Amino acid sequence according to aspect C-18,    comprising or essentially consisting of SEQ ID NO: 5, in which seven    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-20: Amino acid sequence according to aspect C-19,    comprising or essentially consisting of SEQ ID NO: 5, in which eight    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-21: Amino acid sequence according to aspect C-20,    comprising or essentially consisting of SEQ ID NO: 5, in which nine    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-22: Amino acid sequence according to aspect C-21,    comprising or essentially consisting of SEQ ID NO: 5, in which ten    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-23: Amino acid sequence according to aspect C-22,    comprising or essentially consisting of SEQ ID NO: 5, in which    following amino acid residues have been mutated: Val5Leu, Ala14Pro,    Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D.

-   Aspect C-24: Amino acid sequence according to aspect C-13,    comprising or essentially consisting of SEQ ID NO: 5, in which one    or more amino acid residues have been mutated selected from the    following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D.

-   Aspect C-25: Amino acid sequence according to aspect C-13,    comprising or essentially consisting of SEQ ID NO: 5, in which one    or more amino acid residues have been mutated selected from the    following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect C-26: Amino acid sequence according to aspect C-25,    comprising or essentially consisting of SEQ ID NO: 5, in which    following amino acid residues have been mutated: Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D.

-   Aspect C-27: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 5, in which one or more amino acid residues    have been mutated selected from the following: Ala14Pro, Ser19Arg,    Ile20Leu and Gln108Leu.

-   Aspect C-28: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 5, in which one or more amino acid residues    have been mutated selected from the following: Ala14Pro, Ser19Arg,    Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu.

-   Aspect C-29: Amino acid sequence according to aspect C-8, comprising    or essentially consisting of SEQ ID NO: 5, wherein following amino    acid residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

-   Aspect C-30: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 62.

-   Aspect C-31: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 65.

-   Aspect C-32: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 76.

-   Aspect C-33: Amino acid sequence comprising or essentially    consisting of any of SEQ ID NO's: 146-153: 76

-   Aspect C-34: Amino acid sequence according to any of aspects C-1 to    C-33, that can specifically bind to protein F of hRSV with a    dissociation constant (K_(D)) of 1000 nM to 1 nM or less, preferably    100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect C-35: Amino acid sequence according to any of aspects C-1 to    C-34, that can specifically bind to protein F of hRSV with a k-rate    of between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵    M⁻¹ s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶M⁻¹ s⁻¹ or more.

-   Aspect C-36: Amino acid sequence according to any of aspects C-1 to    C-35, that can specifically bind to protein F of hRSV with a k_(off)    rate between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a    near irreversible complex with a t_(1/2) of multiple days),    preferably between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect C-37: Amino acid sequence according to any of aspects C-1 to    C-36, that can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 100 nM and 1000 nM, preferably    between 100 nM and 500 nM, or less.

-   Aspect C-38: Amino acid sequence according to any of aspects C-1 to    C-37, that specifically binds antigenic site II on protein F of hRSV    and/or that competes with Synagis® for binding protein F of hRSV.

-   Aspect D-1: Nanobody® that is directed against and/or specifically    binds protein F of hRSV, chosen from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-2: Nanobody® according to aspect D-1, that comprises or    essentially consists of one of SEQ ID NO's: 60-76.

-   Aspect D-3: Nanobody® that is directed against and/or specifically    binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-4: Nanobody® according to any of aspect D-3, that is chosen    from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-5: Nanobody® according to any of aspects D-3 or D-4, that    comprises or essentially consists of one of SEQ ID NO's: 62, 65, 67,    68, 75 and 76.

-   Aspect D-6: Nanobody® that is directed against and/or specifically    binds protein r of hRSV chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-7: Nanobody® according to any of aspect D-6, that is chosen    from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and    -   the amino acid sequence binds protein F of hRSV with the same,        about the same, or a higher affinity (said affinity as measured        by surface plasmon resonance) and/or the amino acid sequence has        the same, about the same, or a higher potency (as defined        herein) compared to the amino acid sequence without the 3, 2 or        1 amino acid difference.

-   Aspect D-8: Nanobody® that is directed against and/or specifically    binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-9: Nanobody according to aspect D-8, that comprises or    essentially consists of one of SEQ ID NO's: 146-153.

-   Aspect D-10: Nanobody that is directed against and/or specifically    binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic add (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-11: Nanobody according to aspect D-10, that is chosen from    the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino add sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect D-12: Nanobody according to any of aspects D-10 or D-11, that    comprises or essentially consists of one of SEQ ID NO's: 146-149 and    151-153.

-   Aspect D-13: Nanobody® comprising or essentially consisting of SEQ    ID NO: 5, in which one or more amino acid residues have been mutated    selected from the following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu,    Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,    Gln108Leu and Gly54D.

-   Aspect D-14: Nanobody® according to aspect D-13, comprising or    essentially consisting of SEQ ID NO: 5, in which two or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-15: Nanobody® according to aspect D-14, comprising or    essentially consisting of SEQ ID NO: 5, in which three or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-16: Nanobody® according to aspect D-150, comprising or    essentially consisting of SEQ ID NO: 5, in which four or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-17: Nanobody® according to aspect D-16, comprising or    essentially consisting of SEQ ID NO: 5, in which five or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, an 108Leu and Gly54D.

-   Aspect D-18: Nanobody® according to aspect D-17, comprising or    essentially consisting of SEQ ID NO: 5, in which six or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-19: Nanobody® according to aspect D-18, comprising or    essentially consisting of SEQ ID NO: 5, in which seven or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-20: Nanobody® according to aspect D-19, comprising or    essentially consisting of SEQ ID NO: 5, in which eight or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-21: Nanobody® according to aspect D-20, comprising or    essentially consisting of SEQ ID NO: 5, in which nine or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-22: Nanobody® according to aspect D-21, comprising or    essentially consisting of SEQ ID NO: 5, in which ten or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-23: Nanobody® according to aspect D-22, comprising or    essentially consisting of SEQ ID NO: 5, in which following amino    acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D.

-   Aspect D-24: Nanobody® according to aspect D-13, comprising or    essentially consisting of SEQ ID NO: 5, in which one or more amino    acid residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D.

-   Aspect D-25: Nanobody® according to aspect D-8, comprising or    essentially consisting of SEQ ID NO: 5, in which one or more amino    acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect D-26: Nanobody® according to aspect D-20, comprising or    essentially consisting of SEQ ID NO: 5, in which following amino    acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D.

-   Aspect D-27: Nanobody® comprising or essentially consisting of SEQ    ID NO: 5, in which one or more amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu and    Gln108Leu.

-   Aspect D-28: Nanobody® comprising or essentially consisting of SEQ    ID NO: 5, in which one or more amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu.

-   Aspect D-29: Nanobody® according to aspect D-13, comprising or    essentially consisting of SEQ ID NO: 5, wherein following amino acid    residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

-   Aspect D-30: Nanobody® comprising or essentially consisting of SEQ    ID NO: 62.

-   Aspect D-31: Nanobody® comprising or essentially consisting of SEQ    ID NO: 65.

-   Aspect D-32: Nanobody® comprising or essentially consisting of SEQ    ID NO: 76.

-   Aspect D-33: Nanobody® comprising or essentially consisting of any    of SEQ ID NO's: 146-153.

-   Aspect D-34: Nanobody® according to any of aspects D-1 to D-33, that    can specifically bind to protein F of hRSV with a dissociation    constant (K_(D)) of 1000 nM to 1 nM or less, preferably 100 nM to 1    nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect D-35: Nanobody® according to any of aspects D-1 to D-34, that    can specifically bind to protein F of hRSV with a k_(on)-rate of    between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹    s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect D-36: Nanobody® according to any of aspects D-1 to D-35, that    can specifically bind to protein F of hRSV with a k_(off) rate    between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days), preferably    between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect D-37: Nanobody® according to any of aspects D-1 to D-36, that    can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 100 nM and 1000 nM, preferably    between 100 nM and 500 nM, or less.

-   Aspect D-38: Nanobody® according to any of aspects D-1 to D-37, that    specifically binds antigenic site II on protein F of hRSV and/or    that competes with Synagis® for binding protein F of hRSV.

-   Aspect W-1: Amino acid sequence according to any of aspects A-1 to    A-29 and C-1 to C-38, that is directed against and/or specifically    binds protein F of hRSV, wherein the amino acid sequence has    Aspartic acid (Asp, D) at position 1 (said position determined    according to Kabat numbering).

-   Aspect W-2: Amino acid sequence that is directed against and/or    specifically binds protein F of hRSV chosen from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect W-3: Amino acid sequence according to aspect W-2, that    comprises or essentially consists of one of SEQ ID NO's: 138-141 and    154-157.

-   Aspect W-4: Amino acid sequence comprising or essentially consisting    of SEQ ID NO: 5, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect W-5: Amino acid sequence comprising or essentially consisting    of SEQ ID NO: 62, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect W-6: Amino acid sequence comprising or essentially consisting    of SEQ ID NO: 65, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect W-7: Amino acid sequence comprising or essentially consisting    of SEQ ID NO: 76, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect W-8: Amino acid sequence comprising or essentially consisting    of SEQ ID NO: 75, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect W-9: Amino acid sequence comprising or essentially consisting    of SEQ ID NO: 147, in which the Glutamic add at position 1 has been    changed into Aspartic acid.

-   Aspect W-10: Amino acid sequence comprising or essentially    consisting of SEQ ID ND: 149, in which the Glutamic acid at position    1 has been changed into Aspartic acid.

-   Aspect W-11: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 153, in which the Glutamic acid at position    1 has been changed into Aspartic acid.

-   Aspect W-12: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 5, in which one or more amino acid residues    have been mutated selected from the following: Val5Leu, Ala14Pro,    Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D, and wherein the Glutamic acid at    position 1 has been changed into Aspartic acid.

-   Aspect W-13: Amino acid sequence according to aspect W-12,    comprising or essentially consisting of SEQ ID NO: 5, in which two    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-14: Amino acid sequence according to aspect W-13,    comprising or essentially consisting of SEQ ID NO: 5, in which three    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-15: Amino acid sequence according to aspect W-14,    comprising or essentially consisting of SEQ ID NO: 5, in which four    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-16: Amino acid sequence according to aspect W-15,    comprising or essentially consisting of SEQ ID NO: 5, in which five    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-17: Amino acid sequence according to aspect W-16,    comprising or essentially consisting of SEQ ID NO: 5, in which six    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-18: Amino acid sequence according to aspect W-17,    comprising or essentially consisting of SEQ ID NO: 5, in which seven    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-19: Amino acid sequence according to aspect W-18,    comprising or essentially consisting of SEQ ID NO: 5, in which eight    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-20: Amino acid sequence according to aspect W-19,    comprising or essentially consisting of SEQ ID NO: 5, in which nine    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-21: Amino acid sequence according to aspect W-20,    comprising or essentially consisting of SEQ ID NO: 5, in which ten    or more amino acid residues have been mutated selected from the    following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and    wherein the Glutamic acid at position 1 has been changed into    Aspartic add.

-   Aspect W-22: Amino acid sequence according to aspect W-21,    comprising or essentially consisting of SEQ ID NO: 5, in which    following amino acid residues have been mutated: Val5Leu, Ala14Pro,    Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D, and wherein the Glutamic acid at    position 1 has been changed into Aspartic acid.

-   Aspect W-23: Amino acid sequence according to aspect W-12,    comprising or essentially consisting of SEQ ID NO: 5, in which one    or more amino acid residues have been mutated selected from the    following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, and wherein the Glutamic acid at position 1    has been changed into Aspartic acid.

-   Aspect W-24: Amino acid sequence according to aspect W-12,    comprising or essentially consisting of SEQ ID NO: 5, in which one    or more amino acid residues have been mutated selected from the    following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and    wherein the glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect W-25: Amino acid sequence according to aspect W-24,    comprising or essentially consisting of SEQ ID NO: 5, in which    following amino acid residues have been mutated: Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D, and wherein the glutamic acid at    position 1 has been changed into Aspartic acid.

-   Aspect W-26: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 5, in which one or more amino acid residues    have been mutated selected from the following: Ala14Pro, Ser19Arg,    Ile20Leu and Gln108Leu, and wherein the Glutamic acid at position 1    has been changed into Aspartic acid.

-   Aspect W-27: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 5, in which one or more amino acid residues    have been mutated selected from the following: Ala14Pro, Ser19Arg,    Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu, and wherein    the Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect W-28: Amino acid sequence according to aspect W-2 or W-3,    comprising or essentially consisting of SEQ ID NO: 5, wherein    following amino acid residues have been mutated:    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

-   Aspect W-29: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 138.

-   Aspect W-30: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 139.

-   Aspect W-31: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 140.

-   Aspect W-32: Amino acid sequence comprising or essentially    consisting of SEQ ID NO: 141.

-   Aspect W-33: Amino acid sequence comprising or essentially    consisting of any of SEQ ID NO's: 154-157.

-   Aspect W-34: Amino acid sequence according to any of aspects W-1 to    W-33, that can specifically bind to protein F of hRSV with a    dissociation constant (K_(D)) of 1000 nM to 1 nM or less, preferably    100 nM to 1 nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect W-35: Amino acid sequence according to any of aspects W-1 to    W-34, that can specifically bind to protein F of hRSV with a    k_(on)-rate of between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably    between 10⁵ M⁻¹ s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹    s⁻¹ or more.

-   Aspect W-36: Amino acid sequence according to any of aspects W-1 to    W-35, that can specifically bind to protein F of hRSV with a k_(off)    rate between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a    near irreversible complex with a t_(1/2) of multiple days),    preferably between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect W-37: Amino acid sequence according to any of aspects W-1 to    W-36, that can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 100 nM and 1000 nM, preferably    between 100 nM and 500 nM, or less.

-   Aspect W-38: Amino acid sequence according to any of aspects W-1 to    W-37, that specifically binds antigenic site II on protein F of hRSV    and/or that competes with Synagis® for binding protein F of hRSV.

-   Aspect X-1: Nanobody® that is directed against and/or specifically    binds protein F of hRSV according to any of aspects B-1 to B-18 and    D-1 to D-38, wherein the Nanobody has Aspartic acid (Asp, D) at    position 1 (said position determined according to Kabat numbering).

-   Aspect X-2: Nanobody® that is directed against and/or specifically    binds protein F of hRSV, chosen from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino add sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino add sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect X-3: Nanobody® according to aspect X-2, that comprises or    essentially consists of one of SEQ ID NO's: 138-141 and 154-157.

-   Aspect X-4: Nanobody® comprising or essentially consisting of SEQ ID    NO: 5, in which Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect X-5: Nanobody® comprising or essentially consisting of SEQ ID    NO: 62, in which Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect X-6: Nanobody® comprising or essentially consisting of SEQ ID    NO: 65, in which Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect X-7: Nanobody® comprising or essentially consisting of SEQ ID    NO: 76, in which Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect X-8: Nanobody® comprising or essentially consisting of SEQ ID    NO: 75, in which Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect X-9: Nanobody® comprising or essentially consisting of SEQ ID    NO: 147, in which Glutamic acid at position 1 has been changed into    Aspartic acid.

-   Aspect X-10: Nanobody® comprising or essentially consisting of SEQ    ID NO: 149, in which Glutamic acid at position 1 has been changed    into Aspartic acid.

-   Aspect X-11: Nanobody® comprising or essentially consisting of SEQ    ID NO: 153, in which Glutamic acid at position 1 has been changed    into Aspartic acid.

-   Aspect X-12: Nanobody® comprising or essentially consisting of SEQ    ID NO: 5, in which one or more amino acid residues have been mutated    selected from the following: Val5Leu, Ala14Pro, Ser19R, Ile20Leu,    Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,    Gln108Leu and Gly54D, and wherein Glutamic acid at position 1 has    been changed into Aspartic acid.

-   Aspect X-13: Nanobody® according to aspect X-12, comprising or    essentially consisting of SEQ ID NO: 5, in which two or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-14: Nanobody® according to aspect X-13, comprising or    essentially consisting of SEQ ID NO: 5, in which three or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-15: Nanobody® according to aspect X-14, comprising or    essentially consisting of SEQ ID NO: 5, in which four or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-16: Nanobody® according to aspect X-15, comprising or    essentially consisting of SEQ ID NO: 5, in which five or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-17: Nanobody® according to aspect X-16, comprising or    essentially consisting of SEQ ID NO: 5, in which six or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-18: Nanobody® according to aspect X-17, comprising or    essentially consisting of SEQ ID NO: 5, in which seven or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-19: Nanobody® according to aspect X-18, comprising or    essentially consisting of SEQ ID NO: 5, in which eight or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-20: Nanobody® according to aspect X-19, comprising or    essentially consisting of SEQ ID NO: 5, in which nine or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-21: Nanobody® according to aspect X-20, comprising or    essentially consisting of SEQ ID NO: 5, in which ten or more amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-22: Nanobody® according to aspect X-21, comprising or    essentially consisting of SEQ ID NO: 5, in which following amino    acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D, and wherein Glutamic acid at    position 1 has been changed into Aspartic acid.

-   Aspect X-23: Nanobody® according to aspect X-12, comprising or    essentially consisting of SEQ ID NO: 5, in which one or more amino    acid residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D, and wherein Glutamic acid at position 1 has been changed    into Aspartic acid.

-   Aspect X-24: Nanobody® according to aspect X-12, comprising or    essentially consisting of SEQ ID NO: 5, in which one or more amino    acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect X-25: Nanobody® according to aspect X-24, comprising or    essentially consisting of SEQ ID NO: 5, in which following amino    acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, and wherein Glutamic acid at position 1 has    been changed into Aspartic acid.

-   Aspect X-26: Nanobody® comprising or essentially consisting of SEQ    ID NO: 5, in which one or more amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu and    Gln108Leu, and wherein Glutamic acid at position 1 has been changed    into Aspartic acid.

-   Aspect X-27: Nanobody® comprising or essentially consisting of SEQ    ID NO: 5, in which one or more amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, and wherein Glutamic acid at    position 1 has been changed into Aspartic acid.

-   Aspect X-28: Nanobody® according to aspect X-2, comprising or    essentially consisting of SEQ ID NO: 5, wherein following amino acid    residues have been mutated:    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

-   Aspect X-29: Nanobody® comprising or essentially consisting of SEQ    ID NO: 138.

-   Aspect X-30: Nanobody® comprising or essentially consisting of SEQ    ID NO: 139.

-   Aspect X-31: Nanobody® comprising or essentially consisting of SEQ    ID NO: 140.

-   Aspect X-32: Nanobody® comprising or essentially consisting of SEQ    ID NO: 141.

-   Aspect X-33: Nanobody® comprising or essentially consisting of any    of SEQ ID NO's: 154-157.

-   Aspect X-34: Nanobody® according to any of aspects X-1 to X-33, that    can specifically bind to protein F of hRSV with a dissociation    constant (K_(D)) of 1000 nM to 1 nM or less, preferably 100 nM to 1    nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect X-35: Nanobody® according to any of aspects X-1 to X-34, that    can specifically bind to protein F of hRSV with a k_(on)-rate of    between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹    s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect X-36: Nanobody® according to any of aspects X-1 to X-35, that    can specifically bind to protein F of hRSV with a k_(off) rate    between 10² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days), preferably    between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect X-37: Nanobody® according to any of aspects X-1 to X-36, that    can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 100 nM and 1000 nM, preferably    between 100 nM and 500 nM, or less.

-   Aspect X-38: Nanobody® according to any of aspects X-1 to X-37, that    specifically binds antigenic site II on protein F of hRSV and/or    that competes with Synagis® for binding protein F of hRSV.

-   Aspect E-1: Polypeptide that comprises or essentially consists of    one or more amino acid sequences according to any of aspects A-1 to    A-29, C-1 to C-38 and W-1 to W-38 and/or one or more Nanobodies®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38, and optionally further comprises one or more other amino acid    binding units, optionally linked via one or more peptidic linkers.

-   Aspect E-2: Polypeptide according to aspect E-1, in which said one    or more other binding units are immunoglobulin sequences.

-   Aspect E-3: Polypeptide according to any of aspects E-1 or E-2, in    which said one or more other binding units are chosen from the group    consisting of domain antibodies, amino acid sequences that are    suitable for use as a domain antibody, single domain antibodies,    amino acid sequences that are suitable for use as a single domain    antibody, “dAb's”, amino acid sequences that are suitable for use as    a dAb, or Nanobodies®.

-   Aspect E-4: Polypeptide according to any of aspects E-1 to E-3, in    which said one or more amino acid sequences are immunoglobulin    sequences.

-   Aspect E-5: Polypeptide according to any of aspects E-1 to E-4, in    which said one or more amino acid sequences are chosen from the    group consisting of domain antibodies, amino acid sequences that are    suitable for use as a domain antibody, single domain antibodies,    amino acid sequences that are suitable for use as a single domain    antibody, “dAb's”, amino add sequences that are suitable for use as    a dAb, or Nanobodies®.

-   Aspect E-6: Polypeptide according to any of aspects E-1 to E-5, that    comprises or essentially consists of one or more Nanobodies®    according to any of aspects B-1 to B-18, D-1 to D-8 and X-1 to X-38    and in which said one or more other binding units are Nanobodies®.

-   Aspect E-7: Polypeptide according to any of aspects E-1 to E-6,    which is a multivalent construct.

-   Aspect E-8: Multivalent polypeptide according to aspect E-7, that    comprises or essentially consists of at least two amino acid    sequences according to any of aspects A-1 to A-29 and C-1 to C-38    and/or Nanobodies® according to any of aspects B-1 to B-18 and D-1    to D-38 and/or at least one amino acid sequence according to any of    aspects W-1 to W-38 and/or at least one Nanobody® according to any    of aspects X-1 to X-38.

-   Aspect E-9: Multivalent polypeptide according to aspect E-8, wherein    said at least two amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-10: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at least a stretch    of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

-   Aspect E-11: Multivalent polypeptide according to any of aspects E-7    to E-10, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at Feast a stretch    of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or 2 higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a) and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).

-   Aspect E-12: Multivalent polypeptide according to any of aspects E-7    to E-11, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at least a stretch    of amino acid residues chosen from the following:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   a second stretch of amino acid residues chosen from the group        consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and a third stretch of amino acid residues chosen from the group        consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-13: Multivalent polypeptide according to any of aspects E-7    to E-12, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102.

-   Aspect E-14: Multivalent polypeptide according to any of aspects E-7    to E-13, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102 and at least one stretch of amino acid residues (CDR sequence)    chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino add sequence comprising said stretch        of amino add residues has the same, about the same, or a higher        potency (as defined herein) compared to the amino acid sequence        comprising said stretch of amino acid residues without the 3, 2        or 1 amino acid difference.

-   Aspect E-15: Multivalent polypeptide according to any of aspects E-7    to E-14, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102 and a CDR1 sequence chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino add        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and a CDR3 sequence chosen from:    -   c) SEQ ID NO: 121;    -   d) a stretch of amino add residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-16: Multivalent polypeptide according to any of aspects E-7    to E-15, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102 and at least one stretch of amino acid residues (CDR sequence)    chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

-   Aspect E-17: Multivalent polypeptide according to any of aspects E-7    to E-16, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® that comprise SEQ ID NO: 98, SEQ    ID NO: 102 and SEQ ID NO: 121.

-   Aspect E-18: Multivalent polypeptide according to any of aspect E-8    to E-17, wherein said at least two amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-19: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-20: Multivalent polypeptide according to aspect E-19,    wherein said at least two amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-21: Multivalent polypeptide according to aspect E-20, that    comprises or essentially consists of at least two identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    60-76.

-   Aspect E-22: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-23: Multivalent polypeptide according to aspect E-22,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 58, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-24: Multivalent polypeptide according to any of aspects    E-22 or E-23, wherein said at least two amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-25: Multivalent polypeptide according to aspect E-24, that    comprises or essentially consists of at least two identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    62, 65, 67, 68, 75 and 76.

-   Aspect E-26: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-27: Multivalent polypeptide according to aspect E-26,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-28: Multivalent polypeptide according to any of aspects    E-26 or E-27, wherein said at least two amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-29: Multivalent polypeptide according to aspect E-28, that    comprises or essentially consists of at least two identical amino    acid sequences and/or Nanobodies® chosen from SEQ ID NO's: 65 and    76.

-   Aspect E-30: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino add sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-31: Multivalent polypeptide according to aspect E-30,    wherein said at least two amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-32: Multivalent polypeptide according to aspect E-31, that    comprises or essentially consists of at least two identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    146-153.

-   Aspect E-33: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least two amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-34: Multivalent polypeptide according to aspect E-33,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO; 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;        -   (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-35: Multivalent polypeptide according to any of aspects    E-33 or E-34, wherein said at least two amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-36: Multivalent polypeptide according to aspect E-35, that    comprises or essentially consists of at least two identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    62, 65, 67, 68, 75, 76, 147, 149 and 153.

-   Aspect E-37: Multivalent polypeptide comprising or essentially    consisting of at least two amino acid sequences and/or Nanobodies®    with SEQ ID NO: 5, in which one or more (such as two, three, four,    five, six, seven, eight or nine, ten, eleven, or twelve) amino acid    residues have been mutated selected from the following: Val5Leu,    Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

-   Aspect E-38: Multivalent polypeptide according to aspect E-37,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D.

-   Aspect E-39: Multivalent polypeptide according to aspect E-37,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more    (such as two, three, four, five, six, seven or eight) amino acid    residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D.

-   Aspect E-40: Multivalent polypeptide according to aspect E-37,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more    (such as two, three, four or five) amino acid residues have been    mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D.

-   Aspect E-41: Multivalent polypeptide according to aspect E-40,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D.

-   Aspect E-42: Multivalent polypeptide comprising or essentially    consisting of at least two amino acid sequences and/or Nanobodies®    with SEQ ID NO: 5, in which one or more (such as two, three or four)    amino acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

-   Aspect E-43: Multivalent polypeptide comprising or essentially    consisting of at least two amino acid sequences and/or Nanobodies®    with SEQ ID NO: 5, in which one or more (such as two, three, four,    five, six or seven) amino acid residues have been mutated selected    from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu.

-   Aspect E-44: Multivalent polypeptide according to aspect E-37,    comprising or essentially consisting of at least two amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which following    amino acid residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

-   Aspect E-45: Multivalent polypeptide according to aspect E-7, that    comprises or essentially consists of at least three amino acid    sequences according to any of aspects A-1 to A-29, C-1 to C-38 and    W-1 to W-38 and/or Nanobodies® according to any of aspects B-1 to    B-18, D-1 to D-38 and X-1 to X-38.

-   Aspect E-46: Multivalent polypeptide according to aspect E-45,    wherein said at least three amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-47: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise at least a    stretch of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

-   Aspect E-48: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise at least a    stretch of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a) and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).

-   Aspect E-49: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise at least a    stretch of amino acid residues chosen from the following:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   a second stretch of amino acid residues chosen from the group        consisting of:    -   c) SEQ ID NO: 102; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino add            difference;    -   and a third stretch of amino acid residues chosen from the group        consisting of:    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-50: Multivalent polypeptide according to any of aspects    E-45 to E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise at least SEQ    ID NO: 102.

-   Aspect E-51: Multivalent polypeptide according to any of aspects    E-45 to E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise at least SEQ    ID NO: 102 and at least one stretch of amino acid residues (CDR    sequence) chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-52: Multivalent polypeptide according to any of aspects    E-45 to E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprises at least SEQ    ID NO: 102 and a CDR1 sequence chosen from:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and a CDR3 sequence chosen from:    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-53: Multivalent polypeptide according to any of aspects    E-45 to E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise at least SEQ    ID NO: 102 and at least one stretch of amino acid residues (CDR    sequence) chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

-   Aspect E-54: Multivalent polypeptide according to any of aspects    E-45 to E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® that comprise SEQ ID NO: 98,    SEQ ID NO: 102 and SEQ ID NO: 121.

-   Aspect E-55: Multivalent polypeptide according to any of aspect E-47    to E-53, wherein said at least three amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-56: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 60-75;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-57: Multivalent polypeptide according to aspect E-56,    wherein said at least three amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-58: Multivalent polypeptide according to aspect E-57, that    comprises or essentially consists of at least three identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    60-76.

-   Aspect E-59: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leo, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-60: Multivalent polypeptide according to aspect E-59,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-61: Multivalent polypeptide according to any of aspects    E-59 or E-60, wherein said at least three amino acid sequences    and/or Nanobodies® are identical.

-   Aspect E-62: Multivalent polypeptide according to aspect E-61, that    comprises or essentially consists of at least three identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    62, 65, 67, 68, 75 and 76.

-   Aspect E-63: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-64: Multivalent polypeptide according to aspect E-63,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-65: Multivalent polypeptide according to any of aspects    E-63 or E-64, wherein said at least three amino acid sequences    and/or Nanobodies® are identical.

-   Aspect E-66: Multivalent polypeptide according to aspect E-65, that    comprises or essentially consists of at least three identical amino    add sequences and/or Nanobodies® chosen from SEQ ID NO's: 65 and 76.

-   Aspect E-67: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-68: Multivalent polypeptide according to aspect E-67,    wherein said at least three amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-69: Multivalent polypeptide according to aspect E-68, that    comprises or essentially consists of at least three identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    146-153.

-   Aspect E-70: Multivalent polypeptide according to any of aspects    E-45 or E-46, comprising or essentially consisting of at least three    amino acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-71: Multivalent polypeptide according to aspect E-70,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-72: Multivalent polypeptide according to any of aspects    E-70 or E-71, wherein said at least three amino acid sequences    and/or Nanobodies® are identical.

-   Aspect E-73: Multivalent polypeptide according to aspect E-72, that    comprises or essentially consists of at least three identical amino    acid sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    62, 65, 67, 68, 75, 76, 147, 149 and 153.

-   Aspect E-74: Multivalent polypeptide comprising or essentially    consisting of at least three amino acid sequences and/or Nanobodies®    with SEQ ID NO: 5, in which one or more (such as two, three, four,    five, six, seven, eight or nine, ten, eleven, or twelve) amino acid    residues have been mutated selected from the following: Val5Leu,    Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

-   Aspect E-75: Multivalent polypeptide according to aspect E-74,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D.

-   Aspect E-76: Multivalent polypeptide according to aspect E-74,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more    (such as two, three, four, five, six, seven or eight amino acid    residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D.

-   Aspect E-77: Multivalent polypeptide according to aspect E-74,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which one or more    (such as two, three, four or five) amino acid residues have been    mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D.

-   Aspect E-78: Multivalent polypeptide according to aspect E-77,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D.

-   Aspect E-79: Multivalent polypeptide comprising or essentially    consisting of at least three amino acid sequences and/or Nanobodies®    with SEQ ID NO: 5, in which one or more (such as two, three or four)    amino acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

-   Aspect E-80: Multivalent polypeptide comprising or essentially    consisting of at least three amino acid sequences and/or Nanobodies®    with SEQ ID NO: 5, in which one or more (such as two, three, four,    five, six or seven) amino acid residues have been mutated selected    from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu.

-   Aspect E-81: Multivalent polypeptide according to aspect E-74,    comprising or essentially consisting of at least three amino acid    sequences and/or Nanobodies® with SEQ ID NO: 5, in which following    amino acid residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,

-   Aspect E-82: Multivalent polypeptide according to any of aspects E-7    to E-9, comprising or essentially consisting of at least one amino    add sequence and/or Nanobody® chosen from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141, provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-83: Multivalent polypeptide according to aspect E-82, that    comprises or essentially consists of at least one amino acid    sequence and/or Nanobody® chosen from one of SEQ ID NO's: 138-141    and 154-157.

-   Aspect E-84: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-85: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 62, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-86: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 65, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-87: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 76, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-88: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 75, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-89: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 147, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-90: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 149, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-91: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 153, in which the Glutamic acid at position 1 has been    changed into Aspartic acid.

-   Aspect E-92: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three, four, five,    six, seven, eight or nine, ten, eleven or twelve) amino acid    residues have been mutated selected from the following: Val5Leu,    Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid.

-   Aspect E-93: Multivalent polypeptide according to aspect E-92,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D, and wherein the Glutamic acid at    position 1 has been changed into Aspartic acid.

-   Aspect E-94: Multivalent polypeptide according to aspect E-92,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more    (such as two three, four, five, six, seven or eight) amino acid    residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D, and wherein the Glutamic acid at position 1 has been changed    into Aspartic acid.

-   Aspect E-95: Multivalent polypeptide according to aspect E-92,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more    (such as two, three, four or five) amino acid residues have been    mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, and wherein the Glutamic acid at position 1    has been changed into Aspartic acid.

-   Aspect E-96: Multivalent polypeptide according to aspect E-95,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, and wherein the Glutamic acid at position 1    has been changed into Aspartic acid.

-   Aspect E-97: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three or four)    amino acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, and wherein the Glutamic    acid at position 1 has been changed into Aspartic acid.

-   Aspect E-98: Multivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three, four, five,    six or seven) amino acid residues have been mutated selected from    the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gln108Leu, and wherein the Glutamic acid at position 1    has been changed into Aspartic acid.

-   Aspect E-99: Multivalent polypeptide according to aspect E-92,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated:    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

-   Aspect E-100: Bivalent polypeptide according to aspect E-7, that    comprises or essentially consists of two amino acid sequences    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38    and/or Nanobodies® according to any of aspects B-1 to B-18, D-1 to    D-38 and X-1 to X-38.

-   Aspect E-101: Bivalent polypeptide according to aspect E-100,    wherein said two amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-102: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least a stretch of    amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

-   Aspect E-103: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least a stretch of    amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino add sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a) and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).

-   Aspect E-104: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least a stretch of    amino acid residues chosen from the following:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   a second stretch of amino acid residues chosen from the group        consisting of:    -   c) SEQ ID NO: 102;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and a third stretch of amino acid residues chosen from the group        consisting of:    -   e) SEQ ID NO: 121;    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-105: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102.

-   Aspect E-106: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102    and at least one stretch of amino acid residues (CDR sequence)    chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-107: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102    and a CDR1 sequence chosen from:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino add residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino add residues without        the 3, 2 or 1 amino acid difference;    -   and a CDR3 sequence chosen from:    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-108: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise at least SEQ ID NO: 102    and at least one stretch of amino acid residues (CDR sequence)    chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

-   Aspect E-109: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® that comprise SEQ ID NO: 98, SEQ ID NO:    102 and SEQ ID NO: 121.

-   Aspect E-110: Bivalent polypeptide according to any of aspect E-102    to E-109, wherein said at least two amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-111: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino add difference        with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino add sequence hinds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-112: Bivalent polypeptide according to aspect E-111,    wherein said two amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-113: Bivalent polypeptide according to aspect E-112, that    comprises or essentially consists of two identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 60-76.

-   Aspect E-114: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-115: Bivalent polypeptide according to aspect E-114,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-116: Bivalent polypeptide according to any of aspects E-114    or E-415, wherein said two amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-117: Bivalent polypeptide according to aspect E-116, that    comprises or essentially consists of two identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 62, 65,    67, 68, 75 and 76.

-   Aspect E-118: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-119: Bivalent polypeptide according to aspect E-118,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-120: Bivalent polypeptide according to any of aspects E-118    or E-119, wherein said two amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-121: Bivalent polypeptide according to aspect E-120, that    comprises or essentially consists of two identical amino acid    sequences and/or Nanobodies® chosen from SEQ ID NO's: 65 and 76.

-   Aspect E-122: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino add            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-123: Bivalent polypeptide according to aspect E-122,    wherein said two amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-124: Bivalent polypeptide according to aspect E-123, that    comprises or essentially consists of two identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    146-153.

-   Aspect E-125: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of two amino acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-126: Bivalent polypeptide according to aspect E-125,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-127: Bivalent polypeptide according to any of aspects E-125    or E-126, wherein said two amino acid sequences and/or Nanobodies®    are identical.

-   Aspect E-128: Bivalent polypeptide according to aspect E-127, that    comprises or essentially consists of two identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 62, 65,    67, 68, 75, 76, 147, 149 and 153.

-   Aspect E-129: Bivalent polypeptide comprising or essentially    consisting of two amino acid sequences and/or Nanobodies® with SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven, eight or nine, ten, eleven or twelve) amino acid residues    have been mutated selected from the following: Val5Leu, Ala14Pro,    Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54Asp.

-   Aspect E-130: Bivalent polypeptide according to aspect E-129,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid    residues have been mutated: Val5Leu, Ala14Pro, Ser19R, Ile20Leu,    Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,    Gln108Leu and Gly54D.

-   Aspect E-131: Bivalent polypeptide according to aspect E-129,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which one or more (two,    three, four, five, six, seven or eight) amino acid residues have    been mutated selected from the following: Ser19R, Ile20Leu,    Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect E-132: Bivalent polypeptide according to aspect E-129,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as    two, three, four or five) amino acid residues have been mutated    selected from the following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln    and Gly54D.

-   Aspect E-133: Bivalent polypeptide according to aspect E-132,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid    residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln    and Gly54D.

-   Aspect E-134: Bivalent polypeptide comprising or essentially    consisting of two amino acid sequences and/or Nanobodies® with SEQ    ID NO: 5, in which one or more (such as two, three or four) amino    acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

-   Aspect E-135: Bivalent polypeptide comprising or essentially    consisting of two amino acid sequences and/or Nanobodies® with SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six    or seven) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gln108Leu.

-   Aspect E-136: Bivalent polypeptide according to aspect E-129,    comprising or essentially consisting of two amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid    residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

-   Aspect E-137: Bivalent polypeptide according to any of aspects E-100    or E-101, comprising or essentially consisting of at least one amino    acid sequence and/or Nanobody® chosen from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-138: Bivalent polypeptide according to aspect E-137, that    comprises or essentially consists of at least one amino acid    sequence and/or Nanobody® chosen from one of SEQ ID NO's: 138-141    and 154-157.

-   Aspect E-139: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-140: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 62, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-141: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 65, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-142: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 76, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-143: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 75, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-144: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 147, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-145: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 149, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-146: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 153, in which the Glutamic acid at position 1 is changed    into Aspartic acid.

-   Aspect E-147: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three, four, five,    six, seven, eight or nine, ten, eleven or twelve) amino acid    residues have been mutated selected from the following: Val5Leu,    Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, wherein the Glutamic    acid at position 1 is changed into Aspartic acid.

-   Aspect E-148: Bivalent polypeptide according to aspect E-147,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D, wherein the Glutamic acid at    position 1 is changed into Aspartic acid.

-   Aspect E-149: Bivalent polypeptide according to aspect E-147,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more    (such as two, three, four, five, six, seven or eight) amino acid    residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D, wherein the Glutamic acid at position 1 is changed into    Aspartic acid.

-   Aspect E-150: Bivalent polypeptide according to aspect E-147,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more    (such as two, three, four or five) amino acid residues have been    mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, wherein the Glutamic acid at position 1 is    changed into Aspartic acid.

-   Aspect E-151: Bivalent polypeptide according to aspect E-150,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, wherein the Glutamic acid at position 1 is    changed into Aspartic acid.

-   Aspect E-152: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three or four)    amino acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, wherein the Glutamic    acid at position 1 is changed into Aspartic acid.

-   Aspect E-153: Bivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three, four, five,    six or seven) amino acid residues have been mutated selected from    the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gln108Leu, wherein the Glutamic acid at position 1 is    changed into Aspartic acid.

-   Aspect E-154: Bivalent polypeptide according to aspect E-147,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated:    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser1.9Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

-   Aspect E-155: Trivalent polypeptide according to aspect E-7, that    comprises or essentially consists of three amino acid sequences    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38    and/or Nanobodies® according to any of aspects B-1 to B-18, D-1 to    D-38 and X-1 to X-38.

-   Aspect E-156: Trivalent polypeptide according to aspect E-155,    wherein said three amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-157: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise at least a stretch    of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference.

-   Aspect E-158: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise at least a stretch    of amino acid residues chosen from the following:    -   a) SEQ ID NO: 102;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino acid sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and at least one stretch is chosen from:    -   c) SEQ ID NO: 98;    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.    -   such that the stretch of amino acid residues that corresponds to        one of a) and b) should always be present in the amino acid        sequence of the invention and such that the second stretch of        amino acid residues is chosen from one of c), d), e) and f).

-   Aspect E-159: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise at least a stretch    of amino acid residues chosen from the following:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   a second stretch of amino acid residues chosen from the group        consisting of:    -   c) SEQ ID NO: 102; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 102, provided that:        -   i) said stretch of amino acid residues has an Aspartic acid            (Asp, D) at position 6 (position 54 determined according to            Kabat numbering); and        -   ii) the amino acid sequence comprising said stretch of amino            acid residues binds protein F of hRSV with the same, about            the same, or a higher affinity (said affinity as measured by            surface plasmon resonance) and/or the amino acid sequence            comprising said stretch of amino acid residues has the same,            about the same, or a higher potency (as defined herein)            compared to the amino add sequence comprising said stretch            of amino acid residues without the 3, 2 or 1 amino acid            difference;    -   and a third stretch of amino acid residues chosen from the group        consisting of:    -   e) SEQ ID NO: 121; and    -   f) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino add residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-160: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102.

-   Aspect E-161: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102 and at least one stretch of amino acid residues (CDR sequence)    chosen from:    -   a) SEQ ID NO: 98;    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-162: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprises at least SEQ ID NO:    102 and a CDR1 sequence chosen from:    -   a) SEQ ID NO: 98; and    -   b) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 98, provided that the amino acid        sequence comprising said stretch of amino acid residues binds        protein F of hRSV with the same, about the same, or a higher        affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference;    -   and a CDR3 sequence chosen from:    -   c) SEQ ID NO: 121; and    -   d) a stretch of amino acid residues that has no more than 3,        preferably no more than 2, more preferably no more than 1 amino        acid difference with SEQ ID NO: 121, provided that the amino        acid sequence comprising said stretch of amino acid residues        binds protein F of hRSV with the same, about the same, or a        higher affinity (said affinity as measured by surface plasmon        resonance) and/or the amino acid sequence comprising said        stretch of amino acid residues has the same, about the same, or        a higher potency (as defined herein) compared to the amino acid        sequence comprising said stretch of amino acid residues without        the 3, 2 or 1 amino acid difference.

-   Aspect E-163: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise at least SEQ ID NO:    102 and at least one stretch of amino acid residues (CDR sequence)    chosen from SEQ ID NO: 98 and SEQ ID NO: 121.

-   Aspect E-164: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® that comprise SEQ ID NO: 98, SEQ    ID NO: 102 and SEQ ID NO: 121.

-   Aspect E-165: Trivalent polypeptide according to any of aspect E-157    to E-164, wherein said at least three amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-166: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-167: Trivalent polypeptide according to aspect E-166,    wherein said three amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-168: Trivalent polypeptide according to aspect E-167, that    comprises or essentially consists of three identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 60-76.

-   Aspect E-169: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-170: Trivalent polypeptide according to aspect E-169,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-171: Trivalent polypeptide according to any of aspects    B-169 or E-170, wherein said three amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-172: Trivalent polypeptide according to aspect S-171, that    comprises or essentially consists of three identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 62, 65,    67, 68, 75 and 76.

-   Aspect E-173; Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-174: Trivalent polypeptide according to aspect E-173,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-175: Trivalent polypeptide according to any of aspects    E-173 or E-174, wherein said three amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-176: Trivalent polypeptide according to aspect E-175, that    comprises or essentially consists of three identical amino acid    sequences and/or Nanobodies® chosen from SEQ ID NO's: 65 and 76.

-   Aspect E-177: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three amino    acid sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-178: Trivalent polypeptide according to aspect E-177,    wherein said three amino acid sequences and/or Nanobodies® are    identical.

-   Aspect E-179: Trivalent polypeptide according to aspect E-178, that    comprises or essentially consists of three identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's:    146-153.

-   Aspect E-180: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of three acid    sequences and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino add sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-181: Trivalent polypeptide according to aspect E-180,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-182: Trivalent polypeptide according to any of aspects    E-180 or E-181, wherein said three amino acid sequences and/or    Nanobodies® are identical.

-   Aspect E-183: Trivalent polypeptide according to aspect E-182, that    comprises or essentially consists of three identical amino acid    sequences and/or Nanobodies® chosen from one of SEQ ID NO's: 62, 65,    67, 68, 75, 76, 147, 149 and 153.

-   Aspect E-184: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven, eight or nine, ten, eleven or twelve) amino acid residues    have been mutated selected from the following: Val5Leu, Ala14Pro,    Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54Asp.

-   Aspect E-185: Trivalent polypeptide according to aspect E-184,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid    residues have been mutated: Val5Leu, Ala14Pro, Ser19R, Ile20Leu,    Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln,    Gln108Leu and Gly54D.

-   Aspect E-186: Trivalent polypeptide according to aspect E-184,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as    two, three, four, five, six, seven or eight) amino add residues have    been mutated selected from the following: Ser19R, Ile20Leu,    Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect E-187: Trivalent polypeptide according to aspect E-184,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which one or more (such as    two, three, four or five) amino acid residues have been mutated    selected from the following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln    and Gly54D.

-   Aspect E-188: Trivalent polypeptide according to aspect E-187,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid    residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln    and Gly54D.

-   Aspect E-189: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 5, in which one or more (such as two, three or four) amino    acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

-   Aspect E-190: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six    or seven) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gln108Leu.

-   Aspect E-191: Trivalent polypeptide according to aspect E-184,    comprising or essentially consisting of three amino acid sequences    and/or Nanobodies® with SEQ ID NO: 5, in which following amino acid    residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

-   Aspect E-192: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 62.

-   Aspect E-193: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 65.

-   Aspect E-194: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 76.

-   Aspect E-195: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 75.

-   Aspect E-196: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 147.

-   Aspect E-197: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 149.

-   Aspect E-198: Trivalent polypeptide comprising or essentially    consisting of three amino acid sequences and/or Nanobodies® with SEQ    ID NO: 153.

-   Aspect E-199: Trivalent polypeptide according to any of aspects    E-155 or E-156, comprising or essentially consisting of at least one    amino acid sequence and/or Nanobody® chosen from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference.

-   Aspect E-200: Trivalent polypeptide according to aspect E-199, that    comprises or essentially consists of at least one amino acid    sequence and/or Nanobody® chosen from one of SEQ ID NO's: 138-141    and 154-157.

-   Aspect E-201: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-202: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 62, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-203: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 65, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-204: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 76, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-205: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 75, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-206: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 147, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-207: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 149, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-208: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 153, in which the Glutamic acid at position 1 as been    changed into Aspartic acid.

-   Aspect E-209: Trivalent polypeptide comprising or essentially    consisting of at least one amino acid sequence and/or Nanobody® with    SEQ ID NO: 5, in which one or more (such as two, three, four, five,    six, seven, eight or nine, ten, eleven or twelve) amino acid    residues have been mutated selected from the following: Val5Leu,    Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein the    Glutamic acid at position 1 as been changed into Aspartic acid.

-   Aspect E-210: Trivalent polypeptide according to aspect E-209,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Val5Leu, Ala14Pro, Ser19R,    Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln, Gln108Leu and Gly54D, and wherein the Glutamic acid at    position 1 as been changed into Aspartic acid.

-   Aspect E-211: Trivalent polypeptide according to aspect E-209,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more    (such as two, three, four, five, six, seven or eight) amino acid    residues have been mutated selected from the following: Ser19R,    Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gly54D, and wherein the Glutamic acid at position 1 as been changed    into Aspartic acid.

-   Aspect E-212: Trivalent polypeptide according to aspect E-209,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which one or more    (such as two, three, four or five) amino acid residues have been    mutated selected from the following: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, and wherein the Glutamic acid at position 1 as    been changed into Aspartic acid.

-   Aspect E-213: Trivalent polypeptide according to aspect E-212,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated: Gly78Leu, Ala83Arg, Asp85Glu,    Arg105Gln and Gly54D, and wherein the Glutamic acid at position 1 as    been changed into Aspartic acid.

-   Aspect E-214: Trivalent polypeptide according to aspect E-209,    comprising or essentially consisting of at least one amino acid    sequence and/or Nanobody® with SEQ ID NO: 5, in which following    amino acid residues have been mutated:    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln.

-   Aspect E-215: Trivalent polypeptide that is directed against and/or    specifically binds protein F of hRSV, chosen from the following    polypeptides:    -   a) SEQ ID NO's: 77-79 and 158;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 77-79 and 158, provided that:        -   i) the amino acid sequences or Nanobodies® encompassed in            said polypeptide have a Glutamine (Gln, Q) at position 105,            a Leucine (Leu, L) at position 78, an Arginine (Arg, R) at            position 83 and/or a Glutamic acid (Glu, E) at position 85            (said positions determined according to Kabat numbering);            and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-215: Trivalent polypeptide according to aspect E-215,    chosen from the following polypeptides:    -   a) SEQ ID NO's: 77-79 and 158;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 77-79 and 158, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Glutamine (Gln, Q) at position 105, a            Leucine (Leu, L) at position 78, an Arginine (Arg, R) at            position 83 and a Glutamic acid (Glu, E) at position 85            (said positions determined according to Kabat numbering);            and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-217: Trivalent polypeptide that is directed against and/or    specifically binds protein F of hRSV, chosen from the following    polypeptides:    -   a) SEQ ID NO: 78 and 79;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 78 and 79, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has an Aspartic acid (Asp, D) at position 54, a            Glutamine (Gln, Q) at position 105, a Leucine (Leu, L) at            position 78, an Arginine (Arg, R) at position 83 and/or a            Glutamic acid (Glu, E) at position 85 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-218: Trivalent polypeptide according to aspect E-217,    chosen from the following polypeptides:    -   a) SEQ ID NO: 78 and 79; or    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 78 and 79, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has an Aspartic acid (Asp, D) at position 54, a            Glutamine (Gln, Q) at position 105, a Leucine (Leu, L) at            position 78, an Arginine (Arg, R) at position 83 and a            Glutamic add (Glu, E) at position 85 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-219: Trivalent polypeptide that is directed against and/or    specifically binds protein F of hRSV, chosen from the following    polypeptides:    -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Praline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20 and            Leucine (Leu, L) at position 108 (said positions determined            according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-220: Trivalent polypeptide according to aspect E-219,    chosen from the following polypeptides:    -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Proline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20 and            Leucine (Leu, L) at position 108; and in addition Arginine            (Arg, R) at position 83, Glutamic acid (Glu, E) at position            85 and/or Glutamine (Gln, Q) at position 105 (said positions            determined according to Kabat numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-221: Trivalent polypeptide according to any of aspects    E-219 or E-220, chosen from the following polypeptides:    -   a) SEQ ID NO's: 159-161;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 159-161, provided that:        -   i) the amino acid sequence or Nanobody® encompassed in said            polypeptide has a Proline (Pro, P) at position 14, Arginine            (Arg, R) at position 19, Leucine (Leu, L) at position 20 and            Leucine (Leu, L) at position 108; and in addition Arginine            (Arg, R) at position 83, Glutamic acid (Glu, E) at position            85 and/or Glutamine (Gln, 4) at position 105 so that when            the polypeptide has no more than 3, preferably no more than            2, more preferably no more than 1 amino acid difference            with:            -   SEQ ID NO: 159, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83 and Glutamine (Gln, 4) at                position 105;            -   SEQ ID NO: 160, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83, Glutamic acid (Glu, E) at                position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 161, the amino acid sequence or Nanobody®                encompassed in said polypeptide preferably has Arginine                (Arg, R) at position 83 and Glutamic acid (Glu, E) at                position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-222: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp.

-   Aspect E-223: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, following amino acid residues have    been mutated: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly,    Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and    Gly54D.

-   Aspect E-224: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three,    four, five, six, seven or eight) amino acid residues have been    mutated selected from the following: Ser19R, Ile20Leu, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect E-225: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three, four    or five) amino acid residues have been mutated selected from the    following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect E-226: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, following amino acid residues have    been mutated: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D.

-   Aspect E-227: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three or    four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu.

-   Aspect E-228: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu.

-   Aspect E-229: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, following amino acid residues have    been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln.

-   Aspect E-230: Trivalent polypeptide comprising or essentially    consist of SEQ ID ND: 77.

-   Aspect E-231: Trivalent polypeptide comprising or essentially    consist of SEQ ID NO: 78.

-   Aspect E-232: Trivalent polypeptide comprising or essentially    consist of SEQ ID ND: 79.

-   Aspect E-233: Trivalent polypeptide comprising or essentially    consist of one of SEQ ID NO's: 159-161.

-   Aspect E-234: Trivalent polypeptide that is directed against and/or    specifically binds protein F of hRSV, chosen from the following    polypeptides:    -   a) SEQ ID NO's: 142-145 and 162-165;    -   b) polypeptides that have no more than 3, preferably no more        than 2, more preferably no more than 1 amino acid difference        with one of SEQ ID NO's: 142-145 and 162-165, provided that:        -   i) the first amino add sequence or Nanobody® encompassed in            said polypeptide has an Aspartic acid (Asp, D) at position            1; and        -   ii) the polypeptide binds protein F of hRSV with the same,            about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the            polypeptide has the same, about the same, or a higher            potency (as defined herein) compared to the polypeptide            without the 3, 2 or 1 amino acid difference.

-   Aspect E-235: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-236: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 77, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-237: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 78, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-238: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 79, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-239: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 158, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-240: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 159, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-241: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 160, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-242: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 161, in which the first Glutamic acid has    been changed into Aspartic acid.

-   Aspect E-243: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein    the first Glutamic acid has been changed into Aspartic acid.

-   Aspect E-244: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, following amino acid residues have    been mutated: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly,    Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and    Gly54D, and wherein the first Glutamic acid has been changed into    Aspartic acid.

-   Aspect E-245: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three,    four, five, six, seven or eight) amino acid residues have been    mutated selected from the following: Ser19R, Ile20Leu, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly540, and wherein the    first Glutamic acid has been changed into Aspartic acid.

-   Aspect E-246: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three, four    or five) amino acid residues have been mutated selected from the    following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and    wherein the first Glutamic acid has been changed into Aspartic acid.

-   Aspect E-247: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, following amino acid residues have    been mutated: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D,    and wherein the first Glutamic acid has been changed into Aspartic    acid.

-   Aspect E-248: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three or    four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, and wherein    the first Glutamic acid has been changed into Aspartic acid.

-   Aspect E-249: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, and wherein the first Glutamic    acid has been changed into Aspartic acid.

-   Aspect E-250: Trivalent polypeptide comprising or essentially    consisting of SEQ ID NO: 53, in which in at least one (preferably in    two, more preferably in all three) Nanobody®/Nanobodies® that    form(s) part of SEQ ID NO: 53, following amino acid residues have    been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,    -   and wherein the first Glutamic acid has been changed into        Aspartic acid.

-   Aspect E-251: Trivalent polypeptide comprising or essentially    consist of SEQ ID NO: 142.

-   Aspect E-252: Trivalent polypeptide comprising or essentially    consist of SEQ ID NO: 143.

-   Aspect E-253: Trivalent polypeptide comprising or essentially    consist of SEQ ID NO: 144.

-   Aspect E-254: Trivalent polypeptide comprising or essentially    consist of SEQ ID NO: 145.

-   Aspect E-255: Trivalent polypeptide comprising or essentially    consist of one of SEQ ID NO's: 162-165

-   Aspect E-256: Polypeptide according to any of aspects E-1 to E-255,    that can specifically bind to protein F of hRSV with a dissociation    constant (K_(D)) of 100 nM to 0.1 nM or less, preferably 10 nM to    0.1 nM or less, more preferably 1 nM to 0.1 nM or less.

-   Aspect E-257: Polypeptide according to any of aspects E-1 to E-256,    that can specifically bind to protein F of hRSV with a k_(on)-rate    of between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵    M⁻¹ s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect E-258: Polypeptide according to any of aspects E-1 to E-257,    that can specifically bind to protein F of hRSV with a k_(off) rate    between 10⁻² s⁻¹ (t_(1/2)2=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days), preferably    between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, more preferably between 5×10⁻³ s⁻¹    and 10⁻⁴ s⁻¹, or lower.

-   Aspect E-259: Polypeptide y according to any of aspects E-1 to    E-258, that can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value between 10 pM and 1000 pM, preferably    between 10 pM and 250 pM, more preferably between 50 pM and 200 pM    or less.

-   Aspect E-260: Polypeptide according to any of aspects E-1 to E-259,    that can neutralize hRSV (for example, as measured in a    microneutralization assay on hRSV Long (such as e.g. described in    Example 6) with an IC50 value that is at least the same and    preferably better, at least ten times better, preferably twenty    times better, more preferably fifty times better, even more    preferably sixty, seventy, eighty or more times better compared to    the IC50 value obtained with Synagis®.

-   Aspect E-261: Polypeptide according to any of aspects E-1 to E-260,    which is a multispecific construct.

-   Aspect F-1: Monovalent construct, comprising or essentially    consisting of one amino acid sequence according to any of aspects    A-1 to A-29, C-1 to C-38 and W-1 to W-38 and/or one Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38.

-   Aspect F-2: Monovalent construct according to aspect F-1, in which    said amino acid sequence is chosen from the group consisting of    domain antibodies, amino acid sequences that are suitable for use as    a domain antibody, single domain antibodies, amino acid sequences    that are suitable for use as a single domain antibody, “dAb's”,    amino acid sequences that are suitable for use as a dAb, or    Nanobodies®.

-   Aspect F-3: Monovalent construct, comprising or essentially    consisting of one Nanobody® according to any of aspects B-1 to B-18,    D-1 to D-38 and X-1 to X-38.

-   Aspect F-4: Monovalent construct, that is chosen from the group    consisting of SEQ ID NO's: 76, SEQ ID NO's: 138-141 and SEQ ID NO's:    146-157.

-   Aspect F-5: Use of a monovalent construct according to any of    aspects F-1 to F-4, in preparing a multivalent polypeptide according    to any of aspects E-1 to E-261.

-   Aspect F-6: Use of a monovalent construct according to aspect F-5,    wherein the monovalent construct is used as a binding domain or    binding unit in preparing a multivalent construct comprising two or    more binding units.

-   Aspect F-7: Use of a monovalent construct according to any of    aspects F-5 or F-6, in preparing a multivalent polypeptide that    preferably exhibits intramolecular binding compared to    intermolecular binding.

-   Aspect F-8: Use of a monovalent construct according to any of    aspects F-5 to F-7, as a binding domain or binding unit in preparing    a multivalent construct, wherein the binding domains or binding    units are linked via a linker such that the multivalent polypeptide    preferably exhibits intramolecular binding compared to    intermolecular binding and/or the multivalent polypeptide can    simultaneously bind all binding site on protein F of hRSV.

-   Aspect F-9: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct is chosen from    the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-10: Use of a monovalent construct according to aspect F-9,    wherein the monovalent construct essentially consists of one of SEQ    ID NO's: 60-76.

-   Aspect F-11: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct is chosen from    the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or a            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-12: Use of a monovalent construct according to aspect F-11,    wherein the monovalent construct is chosen from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76; or    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-13: Use of a monovalent construct according to aspect F-11    or F-12, wherein the monovalent essentially consists of one of SEQ    ID NO: 62, 65, 67, 68, 75 and 76.

-   Aspect F-14: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct is chosen from    the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic add (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference, in preparing a            multivalent polypeptide.

-   Aspect F-15: Use of a monovalent construct according aspect F-14,    wherein the monovalent construct is chosen from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-16: Use of a monovalent construct essentially consisting of    SEQ ID NO: 62 in preparing a multivalent polypeptide.

-   Aspect F-17: Use of a monovalent construct essentially consisting of    SEQ ID NO: 65 in preparing a multivalent polypeptide.

-   Aspect F-18: Use of a monovalent construct essentially consisting of    SEQ ID NO: 76 in preparing a multivalent polypeptide.

-   Aspect F-19: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct is chosen from    the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-20: Use of a monovalent construct according to aspect F-19,    wherein the monovalent construct essentially consists of one of SEQ    ID NO's: 146-153.

-   Aspect F-21: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct is chosen from    the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position            108; and in addition Arginine (Arg, R) at position 83,            Glutamic acid (Glu, E) at position 85 and/or Glutamine            (Gln, Q) at position 105 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-22: Use of a monovalent construct according to aspect F-21,    wherein the monovalent construct is chosen from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-23: Use of a monovalent construct according to aspect F-21    or F-22, wherein the monovalent essentially consists of one of SEQ    ID NO: 146-149 and 151-153.

-   Aspect F-24: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, in preparing    a multivalent polypeptide.

-   Aspect F-25: Use of a monovalent construct according to aspects    F-24, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, in preparing a    multivalent polypeptide.

-   Aspect F-26: Use of a monovalent construct according to aspects    F-24, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven or eight) amino acid residues have been mutated selected from    the following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D, in preparing a multivalent    polypeptide.

-   Aspect F-27: Use of a monovalent construct according to aspects    F-24, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four or five)    amino acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in preparing a    multivalent polypeptide.

-   Aspect F-28: Use of a monovalent construct according to aspects    F-27, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in preparing a    multivalent polypeptide.

-   Aspect F-29: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three    or four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, in preparing    a multivalent polypeptide.

-   Aspect F-30: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, in preparing a multivalent    polypeptide.

-   Aspect F-31: Use of a monovalent construct according to aspects    F-24, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,    -   in preparing a multivalent polypeptide.

-   Aspect F-32: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct is chosen from    the following:    -   a) SEQ ID NO's; 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Gln, Q) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a multivalent polypeptide.

-   Aspect F-33: Use of a monovalent construct according to aspect F-32,    wherein the monovalent construct essentially consists of one of SEQ    ID NO's: 138-141 and 154-157.

-   Aspect F-34: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-35: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 62, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-36: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 65, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-37: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 76, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-38: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 75, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-39: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 147, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-40: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 149, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-41: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 153, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a multivalent    polypeptide.

-   Aspect F-42: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein    the Glutamic acid at position 1 has been changed into Aspartic acid,    in preparing a multivalent polypeptide.

-   Aspect F-43: Use of a monovalent construct according to aspects    F-42, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid, in    preparing a multivalent polypeptide.

-   Aspect F-44: Use of a monovalent construct according to aspects    F-42, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven or eight) amino acid residues have been mutated selected from    the following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D, and wherein the Glutamic acid at    position 1 has been changed into Aspartic acid, in preparing a    multivalent polypeptide.

-   Aspect F-45: Use of a monovalent construct according to aspects    F-42, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four, or five)    amino acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid, in    preparing a multivalent polypeptide.

-   Aspect F-46: Use of a monovalent construct according to aspects    F-42, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid, in    preparing a multivalent polypeptide.

-   Aspect F-47: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three    or four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, and wherein    the Glutamic acid at position 1 has been changed into Aspartic acid,    in preparing a multivalent polypeptide.

-   Aspect F-48: Use of a monovalent construct according to any of    aspects F-5 to F-8, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg, Asp85Glu, Arg105Gln and    Gln108Leu, and wherein the Glutamic acid at position 1 has been    changed into Aspartic acid, in preparing a multivalent polypeptide.

-   Aspect F-49: Use of a monovalent construct according to aspects    F-42, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln,    -   in preparing a multivalent construct.

-   Aspect F-50: Use of two monovalent constructs according to any of    aspects F-1 to F-4 in preparing a bivalent polypeptide.

-   Aspect F-51: Use of two monovalent constructs according to aspect    F-50, in preparing a bivalent construct that preferably exhibits    intramolecular binding compared to intermolecular binding.

-   Aspect F-52: Use of two monovalent constructs according to any of    aspects F-50 to F-51, as a binding domain or binding unit in    preparing a bivalent polypeptide, wherein the binding domains, or    binding units are linked via a linker such that the bivalent    polypeptide preferably exhibits intramolecular binding compared to    intermolecular binding and/or the bivalent polypeptide can    simultaneously bind both binding site on protein F of hRSV.

-   Aspect F-53: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-54: Use of two monovalent constructs according to aspect    F-53, wherein the two monovalent constructs are identical.

-   Aspect F-55: Use of two monovalent constructs according to aspects    F-53 or F-54, wherein the two monovalent constructs essentially    consist of one of SEQ ID NO's: 60-76.

-   Aspect F-56: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or a            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-57: Use of two monovalent constructs according to aspect    F-56, wherein the monovalent constructs are chosen from the    following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino add sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-58: Use of two monovalent constructs according to aspects    F-56 or F-57, wherein the two monovalent constructs are identical.

-   Aspect F-59: Use of two monovalent constructs according to aspect    F-58, wherein the two monovalent constructs essentially consist of    one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76.

-   Aspect F-60: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-61: Use of two monovalent constructs according to aspect    F-60, wherein the monovalent constructs are chosen from the    following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-62: Use of two monovalent constructs according to aspects    F-60 or F-61, wherein the two monovalent constructs are identical.

-   Aspect F-63: Use of two monovalent constructs essentially consisting    of SEQ ID NO: 62 in preparing a bivalent polypeptide.

-   Aspect F-64: Use of two monovalent constructs essentially consisting    of SEQ ID NO: 65 in preparing a bivalent polypeptide.

-   Aspect F-65: Use of two monovalent constructs essentially consisting    of SEQ ID NO: 76 in preparing a bivalent polypeptide.

-   Aspect F-66: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, 1) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-67: Use of two monovalent constructs according to aspect    F-66, wherein the two monovalent constructs are identical.

-   Aspect F-68: Use of two monovalent constructs according to aspects    F-66 or F-67, wherein the two monovalent constructs essentially    consist of one of SEQ ID NO's: 146-153.

-   Aspect F-69: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-70: Use of two monovalent constructs according to aspect    F-69, wherein the monovalent constructs are chosen from the    following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-71: Use of two monovalent constructs according to aspects    F-69 or F-70, wherein the two monovalent constructs are identical.

-   Aspect F-72: Use of two monovalent constructs according to aspect    F-71, wherein the two monovalent constructs essentially consist of    one of SEQ ID NO's: 146-149 and 151-153.

-   Aspect F-73: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, in preparing    a bivalent polypeptide.

-   Aspect F-74: Use of two monovalent constructs according to aspects    F-73, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, in preparing a    bivalent polypeptide.

-   Aspect F-75: Use of two monovalent constructs according to aspects    F-73, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven or eight) amino acid residues have been mutated selected from    the following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D, in preparing a bivalent polypeptide.

-   Aspect F-76: Use of two monovalent constructs according to aspects    F-73, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four or five)    amino acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in preparing a    bivalent polypeptide.

-   Aspect F-77: Use of two monovalent constructs according to aspects    F-76, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino add residues have been mutated:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in preparing a    bivalent polypeptide.

-   Aspect F-78: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three    or four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, in preparing    a bivalent polypeptide.

-   Aspect F-79: Use of two monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, in preparing a bivalent    polypeptide.

-   Aspect F-80: Use of two monovalent constructs according to aspects    F-73, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;        or    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,    -   in preparing a bivalent polypeptide.

-   Aspect F-81: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct is chosen    from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a bivalent polypeptide.

-   Aspect F-82: Use of a monovalent constructs according to aspect    F-81, wherein the monovalent construct essentially consist of one of    SEQ ID NO's: 138-141 and 154-157.

-   Aspect F-83: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-84: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 62, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-85: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 65, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-86: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 76, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-87: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 75, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-88: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 147, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-89: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 149, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-90: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 153, in which the Glutamic acid at position 1    has been changed into Aspartic acid, in preparing a bivalent    polypeptide.

-   Aspect F-91: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein    the Glutamic acid at position 1 has been changed into Aspartic acid,    in preparing a bivalent polypeptide.

-   Aspect F-92: Use of a monovalent constructs according to aspects    F-91, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid, in    preparing a bivalent polypeptide.

-   Aspect F-93: Use of a monovalent constructs according to aspects    F-91, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven or eight) amino acid residues have been mutated selected from    the following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D, and wherein the Glutamic acid at    position 1 has been changed into Aspartic acid, in preparing a    bivalent polypeptide.

-   Aspect F-94: Use of a monovalent constructs according to aspects    F-91, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four or five)    amino acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid, in    preparing a bivalent polypeptide.

-   Aspect F-95: Use of a monovalent constructs according to aspects    F-94, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein the    Glutamic acid at position 1 has been changed into Aspartic acid, in    preparing a bivalent polypeptide.

-   Aspect F-96: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three    or four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, and wherein    the Glutamic acid at position 1 has been changed into Aspartic acid,    in preparing a bivalent polypeptide.

-   Aspect F-97: Use of a monovalent constructs according to any of    aspects F-50 to F-52, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, and wherein the Glutamic acid at    position 1 has been changed into Aspartic acid, in preparing a    bivalent polypeptide.

-   Aspect F-98: Use of a monovalent constructs according to aspects    F-91, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu,        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln,    -   in preparing a bivalent polypeptide.

-   Aspect F-99: Use of three monovalent constructs according to any of    aspects F-1 to F-4 in preparing a trivalent polypeptide.

-   Aspect F-100: Use of three monovalent constructs according to aspect    F-99, in preparing a trivalent construct that preferably exhibits    intramolecular binding compared to intermolecular binding.

-   Aspect F-101: Use of three monovalent construct according to any of    aspects F-99 to F-100, as a binding domain or binding unit in    preparing a trivalent polypeptide, wherein the binding domains or    binding units are linked via a linker such that the trivalent    polypeptide preferably exhibits intramolecular binding compared to    intermolecular binding and/or the trivalent polypeptide can    simultaneously bind all three binding site on protein F of hRSV.

-   Aspect F-102: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 60-76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 60-76, provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-103: Use of three monovalent constructs according to aspect    F-102, wherein the three monovalent constructs are identical.

-   Aspect F-104: Use of three monovalent constructs according to    aspects F-102 or F-103, wherein the three monovalent constructs    essentially consist of one of SEQ ID NO's: 60-76.

-   Aspect F-105: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and/or a            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-106: Use of three monovalent constructs according to aspect    F-105, wherein the monovalent constructs are chosen from the    following:    -   a) SEQ ID NO's: 62, 65, 67, 68, 75 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76,        provided that:        -   i) the amino acid sequence has a Glutamine (Gln, Q) at            position 105, a Leucine (Leu, L) at position 78 and an            Arginine (Arg, R) at position 83 (said positions determined            according to Kabat numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-107: Use of three monovalent constructs according to    aspects F-105 or F-106, wherein the three monovalent constructs are    identical.

-   Aspect F-108: Use of three monovalent constructs according to aspect    F-107, wherein the three monovalent constructs essentially consist    of one of SEQ ID NO's: 62, 65, 67, 68, 75 and 76.

-   Aspect F-109: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and/or an Arginine (Arg, R) at            position 83 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-110: Use of three monovalent constructs according to aspect    F-109, wherein the monovalent constructs are chosen from the    following:    -   a) SEQ ID NO's: 65 and 76;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 65 and 76, provided that:        -   i) the amino acid sequence has an Aspartic acid (Asp, D) at            position 54, a Glutamine (Gln, Q) at position 105, a Leucine            (Leu, L) at position 78 and an Arginine (Arg, R) at position            83 (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-111: Use of three monovalent constructs according to    aspects F-109 or F-110, wherein the three monovalent constructs are    identical.

-   Aspect F-112: Use of three monovalent constructs essentially    consisting of SEQ ID NO: 62 in preparing a trivalent polypeptide.

-   Aspect F-113: Use of three monovalent constructs essentially    consisting of SEQ ID NO: 65 in preparing a trivalent polypeptide.

-   Aspect F-114: Use of three monovalent constructs essentially    consisting of SEQ ID NO: 76 in preparing a trivalent polypeptide.

-   Aspect F-115: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 146-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-153, provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            (said positions determined according to Kabat numbering);            and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-116: Use of three monovalent constructs according to aspect    F-115, wherein the three monovalent constructs are identical.

-   Aspect F-117: Use of three monovalent constructs according to    aspects F-115 or F-116, wherein the three monovalent constructs    essentially consist of one of SEQ ID NO's: 146-153.

-   Aspect F-118: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 146-14.9 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Proline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 (said positions determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-119: Use of three monovalent constructs according to aspect    F-118, wherein the monovalent constructs are chosen from the    following:    -   a) SEQ ID NO's: 146-149 and 151-153;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 146-149 and 151-153,        provided that:        -   i) the amino acid sequence has a Praline (Pro, P) at            position 14, Arginine (Arg, R) at position 19, Leucine            (Leu, L) at position 20 and Leucine (Leu, L) at position 108            and in addition Arginine (Arg, R) at position 83, Glutamic            acid (Glu, E) at position 85 and/or Glutamine (Gln, Q) at            position 105 so that when the amino acid sequence has no            more than 3, preferably no more than 2, more preferably no            more than 1 amino acid difference with:            -   SEQ ID NO: 146, the amino acid sequence preferably has                Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 147, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamine (Gln, Q)                at position 105;            -   SEQ ID NO: 148, the amino add sequence preferably has                Glutamic acid (Glu, E) at position 85 and Glutamine                (Gln, Q) at position 105;            -   SEQ ID NO: 149, the amino acid sequence preferably has                Arginine (Arg, R) at position 83, Glutamic acid (Glu, E)                at position 85 and Glutamine (Gln, Q) at position 105;            -   SEQ ID NO: 151, the amino acid sequence preferably has                Arginine (Arg, R) at position 83;            -   SEQ ID NO: 152, the amino acid sequence preferably has                Glutamic acid (Glu, E) at position 85;            -   SEQ ID NO: 153, the amino acid sequence preferably has                Arginine (Arg, R) at position 83 and Glutamic acid                (Glu, E) at position 85;            -   (said positions determined according to Kabat                numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-120: Use of three monovalent constructs according to    aspects F-118 or F-119, wherein the three monovalent constructs are    identical.

-   Aspect F-121: Use of three monovalent constructs according to aspect    F-120, wherein the three monovalent constructs essentially consist    of one of SEQ ID NO's: 146-149 and 151-153.

-   Aspect F-122: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, in preparing    a trivalent polypeptide.

-   Aspect F-123: Use of three monovalent constructs according to    aspects F-122, wherein the monovalent construct essentially consists    of SEQ ID NO: 5, in which following amino acid residues have been    mutated: Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser,    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, in    preparing a trivalent polypeptide.

-   Aspect F-124: Use of three monovalent constructs according to    aspects F-122, wherein the monovalent construct essentially consists    of SEQ ID NO: 5, in which one or more (such as two, three, four,    five, six, seven or eight) amino acid residues have been mutated    selected from the following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in preparing a trivalent    polypeptide.

-   Aspect F-125: Use of three monovalent constructs according to    aspects F-122, wherein the monovalent construct essentially consists    of SEQ ID NO: 5, in which one or more (such as two, three, four or    five) amino acid residues have been mutated selected from the    following: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in    preparing a trivalent polypeptide.

-   Aspect F-126: Use of three monovalent constructs according to    aspects F-125, wherein the monovalent construct essentially consists    of SEQ ID NO: 5, in which following amino acid residues have been    mutated: Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, in    preparing a trivalent polypeptide.

-   Aspect F-127: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three    or four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, in preparing    a trivalent polypeptide.

-   Aspect F-128: Use of three monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, in preparing a trivalent    polypeptide.

-   Aspect F-129: Use of three monovalent constructs according to    aspects F-122, wherein the monovalent construct essentially consists    of SEQ ID NO: 5, in which following amino acid residues have been    mutated:    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln and Gln108Leu;    -   Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg, Asp85Glu,        Arg105Gln, Gln108Leu and Gly54Asp;    -   Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Gly54Asp;    -   Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Asp85Glu;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and Arg105Gln;    -   Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg, Asp85Glu and        Arg105Gln,    -   in preparing a trivalent polypeptide.

-   Aspect F-130: Use of an amino acid sequence with SEQ ID NO: 62 in    preparing a trivalent polypeptide with SEQ ID NO: 77, wherein an    amino acid sequence with SEQ ID NO: 62 is linked to at least two    further amino acid sequences with SEQ ID NO: 62, via a 15GS linker.

-   Aspect F-131: Use of an amino acid sequence with SEQ ID NO: 65 in    preparing a trivalent polypeptide with SEQ ID NO: 78, wherein an    amino acid sequence with SEQ ID NO: 65 is linked to at least two    further amino acid sequences with SEQ ID NO: 65, via a 15GS linker.

-   Aspect F-132: Use of an amino acid sequence with SEQ ID NO: 76 in    preparing a trivalent polypeptide with SEQ ID NO: 79, wherein an    amino acid sequence with SEQ ID NO: 76 is linked to at least two    further amino acid sequences with SEQ ID NO: 76, via a 15GS linker.

-   Aspect F-133: Use of an amino acid sequence with SEQ ID NO: 75 in    preparing a trivalent polypeptide with SEQ ID NO: 158, wherein an    amino acid sequence with SEQ ID NO: 75 is linked to at least two    further amino acid sequences with SEQ ID NO: 75, via a 15GS linker.

-   Aspect F-134: Use of an amino acid sequence with SEQ ID NO: 147 in    preparing a trivalent polypeptide with SEQ ID NO: 159, wherein an    amino acid sequence with SEQ ID NO: 147 is linked to at least two    further amino acid sequences with SEQ ID NO: 147, via a 15GS linker.

-   Aspect F-135: Use of an amino acid sequence with SEQ ID NO: 149 in    preparing a trivalent polypeptide with SEQ ID NO: 160, wherein an    amino acid sequence with SEQ ID NO: 149 is linked to at least two    further amino acid sequences with SEQ ID NO: 149, via a 15GS linker.

-   Aspect F-136: Use of an amino acid sequence with SEQ ID NO: 153 in    preparing a trivalent polypeptide with SEQ ID NO: 161, wherein an    amino acid sequence with SEQ ID NO: 153 is linked to at least two    further amino acid sequences with SEQ ID NO: 153, via a 15GS linker.

-   Aspect F-137: Use of a monovalent constructs according to any of    aspects F-99 to F-101, wherein the monovalent constructs are chosen    from the following:    -   a) SEQ ID NO's: 138-141 and 154-157;    -   b) amino acid sequences that have no more than 3, preferably no        more than 2, more preferably no more than 1 amino acid        difference with one of SEQ ID NO's: 138-141 and 154-157,        provided that:        -   i) the amino acid sequence has a Aspartic acid (Asp, D) at            position 1 (said position determined according to Kabat            numbering); and        -   ii) the amino acid sequence binds protein F of hRSV with the            same, about the same, or a higher affinity (said affinity as            measured by surface plasmon resonance) and/or the amino acid            sequence has the same, about the same, or a higher potency            (as defined herein) compared to the amino acid sequence            without the 3, 2 or 1 amino acid difference,    -   in preparing a trivalent polypeptide.

-   Aspect F-138: Use of a monovalent constructs according to aspect    F-137, wherein the monovalent construct essentially consist of one    of SEQ ID NO's: 138-141 and 154-157.

-   Aspect F-139: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-140: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 62, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-141: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 65, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-142: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 76, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-143: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 75, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-144: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 147, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-145: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 149, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-146: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 153, in which the Glutamic acid at position 1    is changed into Aspartic acid, in preparing a trivalent polypeptide.

-   Aspect F-147: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six, seven, eight or nine, ten, eleven or twelve) amino    acid residues have been mutated selected from the following:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp, and wherein    the Glutamic acid at position 1 is changed into Aspartic acid, in    preparing a trivalent polypeptide.

-   Aspect F-248: Use of a monovalent construct according to aspects    F-147, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Val5Leu, Ala14Pro, Ser19R, Ile20Leu, Glu44Gly, Ala74Ser, Gly78Leu,    Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54D, and wherein the    Glutamic acid at position 1 is changed into Aspartic acid, in    preparing a trivalent construct.

-   Aspect F-149: Use of a monovalent construct according to aspects    F-147, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four, five, six,    seven or eight) amino acid residues have been mutated selected from    the following: Ser19R, Ile20Leu, Ala74Ser, Gly78Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gly54D, and wherein the Glutamic acid at    position 1 is changed into Aspartic acid, in preparing a trivalent    polypeptide.

-   Aspect F-150: Use of a monovalent construct according to aspects    F-147, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which one or more (such as two, three, four or five)    amino acid residues have been mutated selected from the following:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein the    Glutamic acid at position 1 is changed into Aspartic acid, in    preparing a trivalent polypeptide.

-   Aspect F-151: Use of a monovalent construct according to aspects    F-150, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54D, and wherein the    Glutamic acid at position 1 is changed into Aspartic acid, in    preparing a trivalent polypeptide.

-   Aspect F-152: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three    or four) amino acid residues have been mutated selected from the    following: Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu, and wherein    the Glutamic acid at position 1 is changed into Aspartic acid, in    preparing a trivalent polypeptide.

-   Aspect F-153: Use of a monovalent construct according to any of    aspects F-99 to F-101, wherein the monovalent construct essentially    consists of SEQ ID NO: 5, in which one or more (such as two, three,    four, five, six or seven) amino acid residues have been mutated    selected from the following: Ala14Pro, Ser19Arg, Ile20Leu, Ala83Arg,    Asp85Glu, Arg105Gln and Gln108Leu, and wherein the Glutamic acid at    position 1 is changed into Aspartic acid, in preparing a trivalent    polypeptide.

-   Aspect F-154: Use of a monovalent construct according to aspects    F-147, wherein the monovalent construct essentially consists of SEQ    ID NO: 5, in which following amino acid residues have been mutated:    -   Glu1Asp;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln and Gln108Leu;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu and Arg105Gln;    -   Glu1Asp, Val5Leu, Ala14Pro, Glu44Gly, Gly78Leu, Ala83Arg,        Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Ala83Arg, Asp85Glu, Arg105Gln, Gln108Leu and Gly54Asp;    -   Glu1Asp, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln and Gly54Asp;    -   Glu1Asp and Gly54Asp;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu and Gln108Leu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Ala83Arg;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu and Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Asp85Glu;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg and        Arg105Gln;    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Asp85Glu and        Arg105Gln; or    -   Glu1Asp, Ala14Pro, Ser19Arg, Ile20Leu, Gln108Leu, Ala83Arg,        Asp85Glu and Arg105Gln,    -   in preparing a trivalent construct.

-   Aspect F-155: Use of an amino acid sequence with SEQ ID NO: 138 in    preparing a trivalent polypeptide with SEQ ID NO: 142, wherein an    amino acid sequence with SEQ ID NO: 138 is linked to at least two    further amino acid sequences with SEQ ID NO: 5, via a 15GS linker.

-   Aspect F-156: Use of an amino acid sequence with SEQ ID NO: 139 in    preparing a trivalent polypeptide with SEQ ID NO: 143, wherein an    amino acid sequence with SEQ ID NO: 139 is linked to at least two    further amino acid sequences with SEQ ID NO: 62, via a 15GS linker.

-   Aspect F-157: Use of an amino acid sequence with SEQ ID NO: 140 in    preparing a trivalent polypeptide with SEQ ID NO: 144, wherein an    amino acid sequence with SEQ ID NO: 140 is linked to at least two    further amino acid sequences with SEQ ID NO: 65, via a 15GS linker.

-   Aspect F-158: Use of an amino acid sequence with SEQ ID NO: 141 in    preparing a trivalent polypeptide with SEQ ID NO: 145, wherein an    amino acid sequence with SEQ ID NO: 141 is linked to at least two    further amino acid sequences with SEQ ID NO: 76, via a 15GS linker.

-   Aspect F-159: Use of an amino acid sequence with SEQ ID NO: 154 in    preparing a trivalent polypeptide with SEQ ID NO: 162, wherein an    amino acid sequence with SEQ ID NO: 154 is linked to at least two    further amino acid sequences with SEQ ID NO: 75, via a 15GS linker.

-   Aspect F-160: Use of an amino acid sequence with SEQ ID NO: 155 in    preparing a trivalent polypeptide with SEQ ID NO: 163, wherein an    amino acid sequence with SEQ ID NO: 155 is linked to at least two    further amino acid sequences with SEQ ID NO: 147, via a 15GS linker.

-   Aspect F-161: Use of an amino acid sequence with SEQ ID NO: 156 in    preparing a trivalent polypeptide with SEQ ID NO: 164, wherein an    amino acid sequence with SEQ ID NO: 156 is linked to at least two    further amino acid sequences with SEQ ID NO: 149, via a 15GS linker.

-   Aspect F-162: Use of an amino acid sequence with SEQ ID NO: 157 in    preparing a trivalent polypeptide with SEQ ID NO: 165, wherein an    amino acid sequence with SEQ ID NO: 157 is linked to at least two    further amino acid sequences with SEQ ID NO: 153, via a 15GS linker.

-   Aspect E-262: Polypeptide according to any of aspects E-1 to E-261,    which has an increased half-life, compared to the corresponding    amino acid sequence according to any of aspects A-1 to A-29, C-1 to    C-38 and W-1 to W-38 per se or Nanobody® according to any of aspects    B-1 to B-18, D-1 to D-38 and X-1 to X-38 per se, respectively.

-   Aspect E-263: Polypeptide according to aspects E-262, in which one    or more other binding units provide the polypeptide with increased    half-life, compared to the corresponding amino acid sequence    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38    per se or Nanobody® according to any of aspects B-1 to B-18, D-1 to    D-38 and X-1 to X-38 per se, respectively.

-   Aspect E-264: Polypeptide according to aspects E-262 or E-263, in    which said one or more other binding units that provide the    polypeptide with increased half-life is chosen from the group    consisting of serum proteins or fragments thereof, binding units    that can bind to serum proteins, an Fc portion, and small proteins    or peptides that can bind to serum proteins.

-   Aspect E-265: Polypeptide according to any of aspects E-262 to    E-264, in which said one or more other binding units that provide    the polypeptide with increased half-life is chosen from the group    consisting of human serum albumin or fragments thereof.

-   Aspect E-266: Polypeptide according to any of aspects E-262 to    E-265, in which said one or more other binding units that provides    the polypeptide with increased half-life are chosen from the group    consisting of binding units that can bind to serum albumin (such as    human serum albumin) or a serum immunoglobulin (such as IgG).

-   Aspect E-267: Polypeptide according to any of aspects E-262 to    E-266, in which said one or more other binding units that provides    the polypeptide with increased half-life are chosen from the group    consisting of domain antibodies, amino acid sequences that are    suitable for use as a domain antibody, single domain antibodies,    amino acid sequences that are suitable for use as a single domain    antibody, “dAb's”, amino acid sequences that are suitable for use as    a dAb, or Nanobodies® that can bind to serum albumin (such as human    serum albumin) or a serum immunoglobulin (such as IgG).

-   Aspect E-268: Polypeptide according to any of aspects E-262 to    E-267, in which said one or more other binding units that provides    the polypeptide with increased half-life is a Nanobody® that can    bind to serum albumin (such as human serum albumin) or a serum    immunoglobulin (such as IgG).

-   Aspect E-269: Polypeptide according to any of aspects E-262 to    E-268, that has a serum half-life that is at least 1.5 times,    preferably at least 2 times, such as at least 5 times, for example    at least 10 times or more than 20 times, greater than the half-life    of the corresponding amino acid sequence according to any of aspects    A-1 to A-29, C-1 to C-38 and W-1 to W-38 per se or Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to X-38    per se, respectively.

-   Aspect E-270: Polypeptide according to any of aspects E-262 to    E-269, that has a serum half-life that is increased with more than 1    hours, preferably more than 2 hours, more preferably more than 6    hours, such as more than 12 hours, or even more than 24, 48 or 72    hours, compared to the corresponding amino acid sequence according    to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38 per se or    Nanobody® according to any of aspects B-1 to B-18, D-1 to D-38 and    X-1 to X-38 per se, respectively.

-   Aspect E-271: Polypeptide according to any of aspects E-262 to    E-270, that has a serum half-life in human of at least about 12    hours, preferably at least 24 hours, more preferably at least 48    hours, even more preferably at least 72 hours or more; for example,    of at least 5 days (such as about 5 to 10 days), preferably at least    9 days (such as about 9 to 14 days), more preferably at least about    10 days (such as about 10 to 15 days), or at least about 11 days    (such as about 11 to 16 days), more preferably at least about 12    days (such as about 12 to 18 days or more), or more than 14 days    (such as about 14 to 19 days).

-   Aspect G-1: Compound or construct, that comprises or essentially    consists of one or more amino acid sequences according to any of    aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38 and/or one or more    Nanobodies® according to any of aspects B-1 to B-18, D-1 to D-38 and    X-1 to X-38 and/or one or more polypeptides according to any of    aspects E-1 to E-271, and optionally further comprises one or more    other groups, residues, moieties or binding units, optionally linked    via one or more linkers.

-   Aspect G-2: Compound or construct according to aspect 0-1, in which    said one or more other groups, residues, moieties or binding units    are amino acid sequences.

-   Aspect G-3: Compound or construct according to any of aspects G-1 or    G-2, in which said one or more linkers, if present, are one or more    amino acid sequences.

-   Aspect G-4: Compound or construct according to any of aspects G-1 to    G-3, in which said one or more other groups, residues, moieties or    binding units are immunoglobulin sequences.

-   Aspect G-5: Compound or construct according to any of aspects G-1 to    G-4, in which said one or more other groups, residues, moieties or    binding units are chosen from the group consisting of domain    antibodies, amino acid sequences that are suitable for use as a    domain antibody, single domain antibodies, amino acid sequences that    are suitable for use as a single domain antibody, “dAb's”, amino    acid sequences that are suitable for use as a dAb, or Nanobodies®.

-   Aspect G-6: Compound or construct according to any of aspects G-1 to    G-5, in which said one or more amino acid sequences of the invention    are immunoglobulin sequences.

-   Aspect G-7: Compound or construct according to any of aspects G-1 to    G-6, in which said one or more amino acid sequences of the invention    are chosen from the group consisting of domain antibodies, amino    acid sequences that are suitable for use as a domain antibody,    single domain antibodies, amino acid sequences that are suitable for    use as a single domain antibody, “dAb's”, amino acid sequences that    are suitable for use as a dAb, or Nanobodies®.

-   Aspect G-8: Compound or construct according to any of aspects G-1 to    G-7, that comprises or essentially consists of one or more    Nanobodies® according to any of aspects B-1 to B-18, D-1 to D-38 and    X-1 to X-38, and in which said one or more other groups, residues,    moieties or binding units are Nanobodies®.

-   Aspect G-9: Compound or construct according to any of aspects G-1 to    G-8, which is a multivalent construct.

-   Aspect G-10: Compound or construct according to any of aspects G-1    to G-9, which is a multispecific construct.

-   Aspect G-11: Compound or construct according to any of aspects G-1    to G-10, which has an increased half-life, compared to the    corresponding amino acid sequence according to any of aspects A-1 to    A-29, C-1 to C-38 and W-1 to W-38 per se or Nanobody® according to    any of aspects B-1 to B-18, D-1 to D-38 and X-1 to X-38 per se, or    polypeptide according to any of aspects E-1 to E-271 per se,    respectively.

-   Aspect G-12: Compound or construct according to any of aspects G-1    to G-11, in which said one or more other groups, residues, moieties    or binding units provide the compound or construct with increased    half-life, compared to the corresponding amino acid sequence    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38    per se or Nanobody® according to any of aspects B-1 to B-18, D-1 to    D-38 and X-1 to X-38 per se, or polypeptide according to any of    aspects E-1 to E-271 per se, respectively.

-   Aspect G-13: Compound or construct according to aspect G-12, in    which said one or more other groups, residues, moieties or binding    units that provide the compound or construct with increased    half-life is chosen from the group consisting of serum proteins or    fragments thereof, binding units that can bind to serum proteins, an    Fc portion, and small proteins or peptides that can bind to serum    proteins.

-   Aspect G-14: Compound or construct according to any of aspects G-12    or G-13, in which said one or more other groups, residues, moieties    or binding units that provide the compound or construct with    increased half-life is chosen from the group consisting of human    serum albumin or fragments thereof.

-   Aspect G-15: Compound or construct according to any of aspects G-12    to G-14, in which said one or more other groups, residues, moieties    or binding units that provide the compound or construct with    increased half-life are chosen from the group consisting of binding    units that can bind to serum albumin (such as human serum albumin)    or a serum immunoglobulin (such as IgG).

-   Aspect G-16: Compound or construct according to any of aspects G-12    to G-15, in which said one or more other groups, residues, moieties    or binding units that provides the compound or construct with    increased half-life are chosen from the group consisting of domain    antibodies, amino acid sequences that are suitable for use as a    domain antibody, single domain antibodies, amino acid sequences that    are suitable for use as a single domain antibody, “dAb”'s, amino    acid sequences that are suitable for use as a dAb, or Nanobodies®    that can bind to serum albumin (such as human serum albumin) or a    serum immunoglobulin (such as IgG).

-   Aspect G-17: Compound or construct according to any of aspects G-12    to G-16, in which said one or more other groups, residues, moieties    or binding units that provides the compound or construct with    increased half-life is a Nanobody® that can bind to serum albumin    (such as human serum albumin) or a serum immunoglobulin (such as    IgG).

-   Aspect G-18: Compound or construct according to any of aspects G-11    to G-17, that has a serum half-life that is at least 1.5 times,    preferably at least 2 times, such as at least 5 times, for example    at least 10 times or more than 20 times, greater than the half-life    of the corresponding amino acid sequence according to any of aspects    A-1 to A-29, C-1 to C-38 and W-1 to W-38 per se or Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-30 and X-1 to X-38    per se, or polypeptide according to any of aspects E-1 to E-271 per    se, respectively.

-   Aspect G-19: Compound or construct according to any of aspects G-11    to G-18, that has a serum half-life that is increased with more than    1 hours, preferably more than 2 hours, more preferably more than 6    hours, such as more than 12 hours, or even more than 24, 48 or 72    hours, compared to the corresponding amino acid sequence according    to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38 per se or    Nanobody® according to any of aspects B-1 to B-18, D-1 to D-38 and    X-1 to X-38 per se, or polypeptide according to any of aspects E-1    to E-271 per se, respectively.

-   Aspect G-20: Compound or construct according to any of aspects G-11    to G-19, that has a serum half-life in human of at least about 12    hours, preferably at least 24 hours, more preferably at least 48    hours, even more preferably at least 72 hours or more; for example,    of at least 5 days (such as about 5 to 10 days), preferably at least    9 days (such as about 9 to 14 days), more preferably at least about    10 days (such as about 10 to 15 days), or at least about 11 days    (such as about 11 to 16 days), more preferably at least about 12    days (such as about 12 to 18 days or more), or more than 14 days    (such as about 14 to 19 days).

-   Aspect M-1: Nucleic acid or nucleotide sequence, that encodes an    amino acid sequence according to any of aspects A-1 to A-29, C-1 to    C-30 and W-1 to W-38, a Nanobody® according to any of aspects B-1 to    B-18, D-1 to D-30 and X-1 to X-38, a polypeptide according to any of    aspects E-1 to E-271, a compound or construct according to any of    aspects G-1 to G-20, that is such that it can be obtained by    expression of a nucleic acid or nucleotide sequence encoding the    same, or a monovalent construct according to any of aspects F-1 to    F-4.

-   Aspect M-2: Nucleic acid or nucleotide sequence according to aspect    M-1, that is in the form of a genetic construct.

-   Aspect M-3: Use of a nucleic acid or nucleotide sequence according    to aspect M-1, that encodes a monovalent construct according to any    of aspects F-1 to F-4, for the preparation of a genetic construct    that encodes a multivalent polypeptide according to any of aspects    E-1 to E-271.

-   Aspect M-4: Use of a nucleic acid or nucleotide sequence according    to aspect M-2, wherein the genetic construct encodes a multivalent    (such as a bivalent) construct.

-   Aspect N-1: Host or host cell that expresses, or that under suitable    circumstances is capable of expressing, an amino acid sequence    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to    W-38, a Nanobody® according to any of aspects B-1 to B-18, D-1 to    D-38 and X-1 to X-38, a polypeptide according to any of aspects E-1    to E-271, a compound or construct according to any of aspects G-1 to    G-20, that is such that it can be obtained by expression of a    nucleic acid or nucleotide sequence encoding the same, or a    monovalent construct according to any of aspects F-1 to F-4; and/or    that comprises a nucleic acid or nucleotide sequence according to    aspects M-1 or M-2.

-   Aspect O-1: Composition, comprising at least one amino acid sequence    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to    W-38, Nanobody® according to any of aspects B-1 to B-18, D-1 to D-38    and X-1 to X-38, polypeptide according to any of aspects E-1 to    E-271, compound or construct according to any of aspects G-1 to    G-20, monovalent construct according to any of aspects F-1 to F-4,    or nucleic acid or nucleotide sequence according to aspects M-1 or    M-2.

-   Aspect O-2: Composition according to aspect O-1, which is a    pharmaceutical composition.

-   Aspect O-3: Composition according to aspects O-1 or O-2, which is a    pharmaceutical composition, that further comprises at least one    pharmaceutically acceptable carrier, diluent or excipient and/or    adjuvant, and that optionally comprises one or more further    pharmaceutically active polypeptides and/or compounds.

-   Aspect P-1: Method for producing an amino acid sequence according to    any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38, a polypeptide according to any of aspects E-1 to E-271, a    compound or construct according to any of aspects G-1 to G-20, that    is such that it can be obtained by expression of a nucleic acid or    nucleotide sequence encoding the same, or a monovalent construct    according to any of aspects F-1 to F-4, or a composition according    to any of aspects O-1 to O-3, said method at least comprising the    steps of:    -   a) expressing, in a suitable host cell or host organism or in        another suitable expression system, a nucleic acid or nucleotide        sequence according to aspects M-1 or M-2,    -   optionally followed by:    -   b) isolating and/or purifying the amino acid sequence according        to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, the        Nanobody® according to any of aspects B-1 to B-18, D-1 to D-38        and X-1 to X-38, the polypeptide according to any of aspects E-1        to E-271, the compound or construct according to any of aspects        G-1 to G-20, that is such that it can be obtained by expression        of a nucleic acid or nucleotide sequence encoding the same, or        the monovalent construct according to any of aspects F-1 to F-4,        thus obtained.

-   Aspect P-2: Method for producing an amino acid sequence according to    any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38, a polypeptide according to any of aspects E-1 to K-271, a    compound or construct according to any of aspects G-1 to G-20, that    is such that it can be obtained by expression of a nucleic acid or    nucleotide sequence encoding the same, or a monovalent construct    according to any of aspects F-1 to F-4, or a composition according    to any of aspects O-1 to O-3, said method at least comprising the    steps of:    -   a) cultivating and/or maintaining a host or host cell according        to aspect N-1 under conditions that are such that said host or        host cell expresses and/or produces at least one amino acid        sequence according to any of aspects A-1 to A-29, C-1 to C-38        and W-1 to W-38, Nanobody® according to any of aspects B-1 to        B-18, D-1 to D-38 and X-1 to X-38, a polypeptide according to        any of aspects E-1 to E-271, compound or construct according to        any of aspects G-1 to G-20, that is such that it can be obtained        by expression of a nucleic acid or nucleotide sequence encoding        the same, or monovalent construct according to any of aspects        F-1 to F-4, or composition according to any of aspects O-1 to        O-3,    -   optionally followed by:    -   b) isolating and/or purifying the amino acid sequence according        to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, the        Nanobody® according to any of aspects B-1 to B-18, D-1 to D-38        and X-1 to X-38, the polypeptide according to any of aspects E-1        to E-271, the compound or construct according to any of aspects        G-1 to G-20, that is such that it can be obtained by expression        of a nucleic acid or nucleotide sequence encoding the same, or        the monovalent construct according to any of aspects F-1 to F-4,        or the composition according to aspects O-1 to O-3, thus        obtained.

-   Aspect P-3: Method for preparing a bivalent or trivalent polypeptide    according to any of aspects E-7 to E-261, said method comprising at    least the steps of linking two or more monovalent amino acid    sequences or monovalent construct according to any of aspects F-1 to    F-4 and for example one or more linkers.

-   Aspect P-4: Method according to aspect P-3, comprising the steps of:    -   a) linking two or more nucleic acid sequences according to        aspect M-1, encoding a monovalent construct according to any of        aspects F-1 to F-4 (and also for example nucleic acids encoding        one or more linkers and further one or more further elements of        genetic constructs known per se) to obtain a genetic construct        according to aspect M-2;    -   b) expressing, in a suitable host cell or host organism or in        another suitable expression system, the genetic construct        obtained in a)    -   optionally followed by:    -   c) isolating and/or purifying the bivalent or trivalent        polypeptide according to any of aspects E-7 to E-261, thus        obtained.

-   Aspect Q-1: Method for screening amino acid sequences directed    against protein F of hRSV, said method comprising at least the steps    of:    -   a. providing a set, collection or library of nucleic acid        sequences encoding amino acid sequences;    -   b. screening said set, collection or library of nucleic acid        sequences for nucleic acid sequences that encode an amino acid        sequence that can bind to and/or has affinity for an envelope        protein of a virus and that is cross-blocked or is cross        blocking a Nanobody® of the invention, e.g. one of SEQ ID NO's:        60-76, 138-141 and 146-157 (Table A-4), or a polypeptide or        construct comprising at least one Nanobody® of the invention,        e.g. a polypeptide or construct comprising at least one of SEQ        ID NO: 77-99, 142-145 and 158-165 (see Table A-5); and    -   c. isolating said nucleic acid sequence, followed by expressing        said amino acid sequence.

-   Aspect R-1: Method for the prevention and/or treatment of hRSV    infection, said method comprising administering, to a subject in    need thereof, a pharmaceutically active amount of at least one amino    acid sequence according to any of aspects A-1 to A-29, C-1 to C-30    and W-1 to W-38, Nanobody® according to any of aspects B-1 to B-18,    D-1 to D-38 and X-1 to X-38, polypeptide according to any of aspects    E-1 to E-271, compound or construct according to any of aspects G-1    to G-20, monovalent construct according to any of aspects F-1 to F-4    and/or composition according to aspects O-1 to O-3.

-   Aspect R-2: Method for the prevention and/or treatment of at least    one of respiratory illness, upper respiratory tract infection, lower    respiratory tract infection, bronchiolitis (inflammation of the    small airways in the lung), pneumonia, dyspnea, cough, (recurrent)    wheezing and asthma, said method comprising administering, to a    subject in need thereof, a pharmaceutically active amount of at    least one amino acid sequence according to any of aspects A-1 to    A-29, C-1 to C-38 and W-1 to W-38, Nanobody® according to any of    aspects B-1 to B-18, D-1 to D-38 and X-1 to X-38, polypeptide    according to any of aspects E-1 to E-271, compound or construct    according to any of aspects G-1 to G-20, monovalent construct    according to any of aspects F-1 to F-4 and/or composition according    to aspects O-1 to O-3.

-   Aspect R-3: Method for the prevention and/or treatment of at least    one disease or disorder that can be prevented and/or treated by    administering, to a subject in need thereof, an amino acid sequence    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to    W-38, a Nanobody® according to any of aspects B-1 to B-18, D-1 to    D-38 and X-1 to X-38, a polypeptide according to any of aspects E-1    to E-271, a compound or construct according to any of aspects G-1 to    G-20, a monovalent construct according to any of aspects F-1 to F-4    and/or a composition according to aspects O-1 to O-3, said method    comprising administering, to a subject in need thereof, a    pharmaceutically active amount of at least one amino acid sequence    according to any of aspects A-1 to A-29, C-1 to C-38 and W-1 to    W-38, Nanobody® according to any of aspects B-1 to B-18, D-1 to F-38    and X-1 to X-38, polypeptide according to any of aspects E-1 to    E-271, compound or construct according to any of aspects G-1 to    G-20, monovalent construct according to any of aspects F-1 to F-4    and/or composition according to aspects O-1 to O-3.

-   Aspect R-4: Method for immunotherapy, said method comprising    administering, to a subject in need thereof, a pharmaceutically    active amount of at least one amino acid sequence according to any    of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38, polypeptide according to any of aspects E-1 to E-271, compound    or construct according to any of aspects G-1 to G-20, monovalent    construct according to any of aspects F-1 to F-4 and/or composition    according to aspects O-1 to O-3.

-   Aspect R-5: Use of an amino acid sequence according to any of    aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38, a polypeptide according to any of aspects E-1 to E-271, a    compound or construct according to any of aspects G-1 to G-20, a    monovalent construct according to any of aspects F-1 to F-4 and/or    composition according to aspects O-1 to O-3 in the preparation of a    pharmaceutical composition for prevention and/or treatment of hRSV    infection; and/or for use in one or more of the methods according to    aspects R-1 to R-4.

-   Aspect R-6: Amino acid sequence according to any of aspects A-1 to    A-29, C-1 to C-38 and W-1 to W-38, Nanobody® according to any of    aspects B-1 to B-18, D-1 to D-38 and X-1 to X-38, polypeptide    according to any of aspects E-1 to E-271, compound or construct    according to any of aspects G-1 to G-20, monovalent construct    according to any of aspects F-1 to F-4 and/or composition according    to aspects O-1 to O-3 for prevention and/or treatment of at least    one of respiratory illness, upper respiratory tract infection, lower    respiratory tract infection, bronchiolitis (inflammation of the    small airways in the lung), pneumonia, dyspnea, cough, (recurrent)    wheezing and asthma.

-   Aspect S-1: Part or fragment of an amino acid sequence according to    any of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38, and/or a polypeptide according to any of aspects E-1 to E-271.

-   Aspect S-2: Part or fragment according to aspect S-1, that can    specifically bind to antigenic II on protein F of hRSV and/or    competes with Synagis® for binding protein F of hRSV.

-   Aspect S-3: Part of fragment according to any of aspects S-1 to S-2,    that can specifically bind to protein F of hRSV with a dissociation    constant (K_(D)) of 1000 nM to 1 nM or less, preferably 100 nM to 1    nM or less, more preferably 10 nM to 1 nM or less.

-   Aspect S-4: Part or fragment according to any of aspects S-2 to S-3,    that can specifically bind to protein F of hRSV with a k_(on)-rate    of between 10⁴M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵    M⁻¹ s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect S-5: Part or fragment according to any of aspects S-2 to S-4    that can specifically bind to protein F of hRSV with a k_(off) rate    between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days, preferably    between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect S-6: Compound or construct, that comprises or essentially    consists of one or more parts or fragments according to any of    aspects S-1 to S-5, and optionally further comprises one or more    other groups, residues, moieties or binding units, optionally linked    via one or more linkers.

-   Aspect S-7: Compound or construct according to aspect S-6, in which    said one or more other groups, residues, moieties or binding units    are amino acid sequences.

-   Aspect S-8: Compound or construct according to aspects S-6 or S-7,    in which said one or more linkers, if present, are one or more amino    acid sequences.

-   Aspect S-9: Nucleic acid or nucleotide sequence, that encodes a part    or fragment according to any of aspects S-1 to S-5 or a compound or    construct according to any of aspects S-6 to S-8.

-   Aspect S-10: Composition, comprising at least one part or fragment    according to any of aspects S-1 to S-5, compound or construct    according to any of aspects S-6 to S-8, or nucleic acid or    nucleotide sequence according to aspect S-9.

-   Aspect T-1: Derivative of an amino acid sequence according to any of    aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38 or of a Nanobody®    according to any of aspects B-1 to B-18, D-1 to D-38 and X-1 to    X-38.

-   Aspect T-2: Derivative according to aspect T-1, that can    specifically bind to antigenic site II on protein F of hRSV and/or    compete with Synagis® for binding protein F of hRSV.

-   Aspect T-3: Derivative according to any of aspects T-1 to T-2, that    can specifically bind to protein F of hRSV with a k_(on)-rate of    between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹    s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect T-4: Derivative according to any of aspects T-2 to T-3, that    can specifically bind to protein F of hRSV with a k_(off)-rate of    between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹    s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect T-5: Derivative according to any of aspects T-2 to T-4, that    can specifically bind to protein F of hRSV with a k_(off) rate    between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days), preferably    between 10⁻³ s¹ and 10⁻⁴ s⁻¹, or lower.

-   Aspect T-6: Derivative of a compound or construct according to any    of aspects G-1 to G-20 or a polypeptide according to any of aspects    E-1 to E-271.

-   Aspect T-7: Derivative according to aspect T-6, that can    specifically bind to antigenic site II on protein F of hRSV and/or    compete with Synagis® for binding protein F of hRSV.

-   Aspect T-8: Derivative according to any of aspects T-6 to T-7, that    can specifically bind to protein F of hRSV with a dissociation    constant (K_(D)) of 100 nM to 0.1 nM or less, preferably 10 nM to    0.1 nM or less, more preferably 1 nM to 0.1 nM or less.

-   Aspect T-9: Derivative according to any of aspects T-6 to T-8, that    can specifically bind to protein F of hRSV with a k_(on)-rate of    between 10⁴ M⁻¹ s⁻¹ to about 10⁷ M⁻¹ s⁻¹, preferably between 10⁵ M⁻¹    s⁻¹ and 10⁷ M⁻¹ s⁻¹, more preferably about 10⁶ M⁻¹ s⁻¹ or more.

-   Aspect T-10: Derivative according to any of aspects T-6 to T-9, that    can specifically bind to protein F of hRSV with a k_(off) rate    between 10⁻² s⁻¹ (t_(1/2)=0.69 s) and 10⁻⁴ s⁻¹ (providing a near    irreversible complex with a t_(1/2) of multiple days), preferably    between 10⁻³ s⁻¹ and 10⁻⁴ s⁻¹, more preferably between 5×10⁻³ s⁻¹    and 10⁻⁴ s⁻¹, or lower.

-   Aspect T-11: Derivative according to any of aspects T-6 to T-10,    that can neutralize hRSV, e.g. in a microneutralization assay of RSV    strain Long (such as e.g. described in Example 6), with an IC50    value between 10 pM and 1000 pM, preferably between 10 pM and 250    pM, more preferably between 50 pM and 200 pM or less.

-   Aspect T-12: Derivative according to any of aspects T-6 to T-11,    that can neutralize hRSV, e.g. in a microneutralization assay of RSV    strain Long (such as e.g. described in Example 6), with an IC50    value that is at least the same and preferably better, at least ten    times better, preferably twenty times better, more preferably fifty    times better, even more preferably sixty, seventy, eighty or more    times better compared to the IC50 value obtained with Synagis®.

-   Aspect T-13: Derivative according to any of aspects T-1 to T-12,    that has a serum half-life that is at least 1.5 times, preferably at    least 2 times, such as at least 5 times, for example at least 10    times or more than 20 times, greater than the half-life of the    corresponding amino acid sequence according to any of aspects A-1 to    A-29, C-1 to C-38 and W-1 to W-38 per se, Nanobody® according to any    of aspects B-1 to B-18, D-1 to D-38 and X-1 to X-38 per se,    polypeptide according to any of aspects E-1 to E-261, compound or    construct according to any of aspects G-1 to G-20 per se, or    monovalent construct according to any of aspects F-1 to F-4 per se,    respectively.

-   Aspect T-14: Derivative according to any of aspects T-1 to T-13,    that has a serum half-life that is increased with more than 1 hours,    preferably more than 2 hours, more preferably more than 6 hours,    such as more than 12 hours, or even more than 24, 48 or 72 hours,    compared to the corresponding amino acid sequence according to any    of aspects A-1 to A-29, C-1 to C-38 and W-1 to W-38 per se,    Nanobody® according to any of aspects B-1 to B-18, D-1 to D-38 and    X-1 to X-38 per se, polypeptide according to any of aspects E-1 to    E-261, compound or construct according to any of aspects G-1 to G-20    per se, or monovalent construct according to any of aspects F-1 to    F-4 per se, respectively.

-   Aspect T-15: Derivative according to any of aspects T-1 to T-14,    that has a serum half-life in human of at least about 12 hours,    preferably at least 24 hours, more preferably at least 48 hours,    even more preferably at least 72 hours or more; for example, at    least 5 days (such as about 5 to 10 days), preferably at least 9    days (such as about 9 to 14 days), more preferably at least about 10    days (such as about 10 to 15 days), or at least about 11 days (such    as about 11 to 16 days), more preferably at least about 12 days    (such as about 12 to 18 days or more), or more than 14 days (such as    about 14 to 19 days).

-   Aspect T-16: Derivative according to any of aspects T-1 to T-15,    that is a pegylated derivative.

-   Aspect T-17: Compound or construct, that comprises or essentially    consists of one or more derivatives according to any of aspects T-1    to T-16, and optionally further comprises one or more other groups,    residues, moieties or binding units, optionally linked via one or    more linkers.

-   Aspect T-18: Compound or construct according to aspect T-17, in    which said one or more other groups, residues, moieties or binding    units are amino acid sequences.

-   Aspect T-19: Compound or construct according to aspects T-17 or    T-18, in which said one or more linkers, if present, are one or more    amino acid sequences.

-   Aspect T-20: Nucleic acid or nucleotide sequence, that encodes a    derivative according to any of aspects T-1 to T-16 or a compound or    construct according to any of aspects T-17 to T-19.

-   Aspect T-21: Composition, comprising at least one derivative    according to any of aspects T-1 to T-16, compound or construct    according to any of aspects T-17 to T-19, or nucleic acid or    nucleotide sequence according to aspect T-20.

-   Aspect U-1: A method for administering an effective amount of an    amino acid sequence according to any of claims A-1 to A-29, C-1 to    C-38 and W-1 to W-38, a Nanobody® according to any of claims B-1 to    B-18, D-1 to D-38 and X-1 to X-38, a polypeptide according to any of    claims E-1 to E-271, a compound or construct according to any of    claims G-1 to G-20 and/or a monovalent construct according to any of    claims F-1 to F-4, and/or a composition comprising the same, wherein    said method comprises the step of administering the amino acid    sequence according to any of claims A-1 to A-29, C-1 to C-38 and W-1    to W-38, the Nanobody® according to any of claims B-1 to B-18, D-1    to D-38 and X-1 to X-38, the polypeptide according to any of claims    E-1 to E-271, the compound or construct according to any of claims    G-1 to G-20 and/or the monovalent construct according to any of    claims F-1 to F-4, and/or a composition comprising the same to the    pulmonary tissue.

-   Aspect U-2: The method according to aspect U-1, wherein the amino    acid sequence according to any of claims A-1 to A-29, C-1 to C-38    and W-1 to W-38, the Nanobody® according to any of claims B-1 to    B-18, D-1 to D-38 and X-1 to X-38, the polypeptide according to any    of claims E-1 to E-271, the compound or construct according to any    of claims G-1 to G-20 and/or the monovalent construct according to    any of claims F-1 to F-4, and/or a composition comprising the same    is administered by use of an inhaler, intranasal delivery device or    aerosol.

-   Aspect U-3: Method according to any of aspects U-1 or U-2, wherein    at least 5%, preferably at least 10%, 20%, 30%, 40%, more preferably    at least 50%, 60%, 70%, and even more preferably at least 80% or    more of the amino acid sequence according to any of claims A-1 to    A-29, C-1 to C-38 and W-1 to W-38, the Nanobody® according to any of    claims B-1 to B-18, D-1 to D-38 and X-1 to X-38, the polypeptide    according to any of claims E-1 to E-271, the compound or construct    according to any of claims G-1 to G-20 and/or the monovalent    construct according to any of claims F-1 to F-4, and/or a    composition comprising the same is stable in the pulmonary tissue    for at least 24 hours, preferably at least 48 hours more preferably    at least 72 hours.

-   Aspect U-4: Method according to any of aspects U-1 to U-3, wherein    the amino acid sequence according to any of claims A-1 to A-29, C-1    to C-38 and W-1 to W-38, the Nanobody® according to any of claims    B-1 to B-18, D-1 to D-38 and X-1 to X-38, the polypeptide according    to any of claims E-1 to E-271, the compound or construct according    to any of claims G-1 to G-20 and/or the monovalent construct    according to any of claims F-1 to F-4, and/or a composition    comprising the same are applied in pure form, i.e., when they are    liquids or a dry powder.

-   Aspect U-5: Method according to any of aspects U-1 to U-3, wherein    the amino acid sequence according to any of claims A-1 to A-29, C-1    to C-38 and W-1 to W-38, the Nanobody® according to any of claims    B-1 to B-18, D-1 to D-38 and X-1 to X-38, the polypeptide according    to any of claims E-1 to E-271, the compound or construct according    to any of claims G-1 to G-20 and/or the monovalent construct    according to any of claims F-1 to F-4, and/or a composition    comprising the same are administered to the pulmonary tissue as    composition or formulation comprising an amino acid sequence    according to any of claims A-1 to A-29, C-1 to C-38 and W-1 to W-38,    a Nanobody® according to any of claims B-1 to B-18, D-1 to D-38 and    X-1 to X-38, a polypeptide according to any of claims E-1 to E-271,    a compound or construct according to any of claims G-1 to G-20    and/or a monovalent construct according to any of claims F-1 to F-4,    and a carrier suitable for pulmonary delivery.

-   Aspect U-6; Pharmaceutical composition comprising an amino add    sequence according to any of claims A-1 to A-29, C-1 to C-38 and W-1    to W-38, a Nanobody® according to any of claims B-1 to B-18, D-1 to    D-38 and X-1 to X-38, a polypeptide according to any of claims E-1    to E-271, a compound or construct according to any of claims G-1 to    G-20 and/or a monovalent construct according to any of claims F-1 to    F-4, and a carrier suitable for pulmonary delivery.

-   Aspect U-7: Pharmaceutical device suitable for the pulmonary    delivery of an amino acid sequence according to any of claims A-1 to    A-29, C-1 to C-38 and W-1 to W-38, a Nanobody® according to any of    claims B-1 to B-18, D-1 to D-38 and X-1 to X-38, a polypeptide    according to any of claims E-1 to E-271, a compound or construct    according to any of claims G-1 to G-20 and/or a monovalent construct    according to any of claims F-1 to F-4 and/or suitable in the use of    a composition comprising the same.

-   Aspect U-8: Pharmaceutical device according to aspect U-7 that is an    inhaler for liquids (e.g. a suspension of fine solid particles or    droplets) comprising an amino acid sequence according to any of    claims A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody®    according to any of claims B-1 to B-18, D-1 to D-38 and X-1 to X-38,    a polypeptide according to any of claims E-1 to E-271, a compound or    construct according to any of claims G-1 to G-20 and/or a monovalent    construct according to any of claims F-1 to F-4.

-   Aspect U-9: Pharmaceutical device according to aspect U-7 that is an    aerosol comprising an amino acid sequence according to any of claims    A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody® according to    any of claims B-1 to B-18, D-1 to D-38 and X-1 to X-38, a    polypeptide according to any of claims E-1 to E-271, a compound or    construct according to any of claims G-1 to G-20 and/or a monovalent    construct according to any of claims F-1 to F-4.

-   Aspect U-10: Pharmaceutical device according to aspect U-7 that is a    dry powder inhaler comprising an amino acid sequence according to    any of claims A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody®    according to any of claims B-1 to B-18, D-1 to D-38 and X-1 to X-38,    a polypeptide according to any of claims E-1 to E-271, a compound or    construct according to any of claims G-1 to G-20 and/or a monovalent    construct according to any of claims F-1 to F-4 in the form of a dry    powder.

-   Aspect U-11: Method for the prevention and/or treatment of hRSV    infection, said method comprising administering to the pulmonary    tissue of a subject in need thereof, a pharmaceutically active    amount of an amino acid sequence according to any of claims A-1 to    A-29, C-1 to C-38 and W-1 to W-38, a Nanobody® according to any of    claims B-1 to B-18, D-1 to D-38 and X-1 to X-38, a polypeptide    according to any of claims E-1 to E-271, a compound or construct    according to any of claims G-1 to G-20 and/or a monovalent construct    according to any of claims F-1 to F-4 and/or of a pharmaceutical    composition comprising the same.

-   Aspect U-12: Method for the prevention and/or treatment of    respiratory illness, upper respiratory tract infection, lower    respiratory tract infection, bronchiolitis (inflammation of the    small airways in the lung), pneumonia, dyspnea, cough, (recurrent)    wheezing and asthma, said method comprising administering to the    pulmonary tissue of a subject in need thereof, a pharmaceutically    active amount of an amino acid sequence according to any of claims    A-1 to A-29, C-1 to C-38 and W-1 to W-38, a Nanobody® according to    any of claims B-1 to B-18, D-1 to D-38 and X-1 to X-38, a    polypeptide according to any of claims E-1 to E-271, a compound or    construct according to any of claims G-1 to G-20 and/or a monovalent    construct according to any of claims F-1 to F-4, and/or of a    pharmaceutical composition comprising the same.

-   Aspect V-1: Method for the prevention and/or treatment of hRSV    infection, said method comprising administering, to a subject in    need thereof, a pharmaceutically active amount of a multivalent    polypeptide according to any of aspects E-7 to E-261, and/or of a    pharmaceutical composition comprising the same.

-   Aspect V-2: Use of a multivalent polypeptide according to any of    aspects E-7 to E-261, and/or of a pharmaceutical composition    comprising the same for binding and/or neutralization of hRSV.

-   Aspect V-3: Use of a multivalent polypeptide according to any of    aspects E-7 to E-261, and/or of a pharmaceutical composition    comprising the same for binding and/or neutralization of different    strains of hRSV.

-   Aspect V-4: Use of a multivalent polypeptide according to any of    aspects E-7 to E-261, and/or of a pharmaceutical composition    comprising the same for binding and/or neutralization of one or more    escape mutants of a virus.

-   Aspect V-5: Method or use according to any of aspects V-1 to V-4,    wherein the multivalent polypeptide is bivalent.

-   Aspect V-6: Method or use according to any of aspects V-1 to V-4,    wherein the multivalent polypeptide is trivalent.

-   Aspect V-7: Method or use according to any of aspects V-1 to V-6,    wherein said multivalent polypeptide is administered according to    any of the methods of claims U-1 to U-5 and/or U-11 to U-12.

-   Aspect V-8: Method for the prevention and/or treatment of infection    by hRSV virus, said method comprising administering, to a subject in    need thereof, a pharmaceutically active amount of a multivalent    polypeptide according to any of aspects E-7 to E-261 and/or of a    pharmaceutical composition comprising the same.

-   Aspect V-9: Method according to aspect V-8 wherein the multivalent    compound or construct is selected from Table A-5 (SEQ ID NO's:    77-99, 138-141 and 146-157).

-   Aspect V-10: Method according to any of aspects V-8 or V-9, wherein    infection by one or more RSV escape mutants is treated.

-   Aspect V-11: Method according to aspect V-10, wherein the escape    mutant is an escape mutant specific for antigenic site II.

-   Aspect V-12: Use of a multivalent compound or construct according to    any of aspects E-7 to E-261, and/or of a pharmaceutical composition    comprising the same for binding and/or neutralization one or more    different escape mutants of RSV.

-   Aspect V-13: Use according to claim V-12 wherein the escape mutant    is an escape mutant specific for antigenic site

-   Aspect V-14: Method according to any of aspects V-8 or V-9, wherein    infection by one or more strains of hRSV is treated.

-   Aspect V-15: Method according to aspect V-14, wherein the RSV strain    is Long.

-   Aspect V-16: Method according to aspect V-14, wherein the RSV strain    is A-2.

-   Aspect V-17: Method according to aspect V-14, wherein the RSV strain    is B-1.

-   Aspect V-18: Method according to aspect V-14, wherein the    multivalent polypeptide binds and/or neutralizes RSV strain Long and    A-2.

-   Aspect V-19: Method according to aspect V-14, wherein the    multivalent polypeptide binds and/or neutralizes RSV strain Long and    B-1.

-   Aspect V-20: Method according to aspect V-14, wherein the    multivalent polypeptide binds and/or neutralizes RSV strain B-1 and    A-2.

-   Aspect V-21: Method according to aspect V-14, wherein the    multivalent polypeptide binds and/or neutralizes RSV strain Long,    A-2 and B-1.

-   Aspect V-22: Use of a multivalent compound or construct according to    any of aspects E-7 to E-261, and/or of a pharmaceutical composition    comprising the same for binding and/or neutralization different    strains of hRSV.

-   Aspect V-23: Use according to aspect V-22, wherein the strains of    RSV are Long and A-2.

-   Aspect V-24: Use according to aspect V-22, wherein the strains of    RSV are Long and B-1.

-   Aspect V-25: Use according to aspect V-22, wherein the strains of    RSV are A-1 and B-1. Aspect V-26: Use according to aspect V-22,    wherein the strains of RSV are Long, A-2 and B-1.

EXAMPLES Example 1 Immunizations

Two llamas (156 and 157) were immunized according to standard protocolswith 6 boosts of hRSV F_(TM)-(membrane anchorless form of the fusionprotein, 70 kDa; Corrall T. et al. 2007, BMC Biotechnol. 7: 17). Bloodwas collected from these animals 7 days after boost 6 and 10 days afterboost 6.

Two llamas (212 and 213) were immunized intramuscularly in the neck with1 mg of RNA-inactivated RSV strain long A (Hytest, Turku Finland;#8RSV79), followed by 4 boosts of 0.5 mg RSV in a biweekly regimen. Twollamas (206 and 207) were immunized intramuscularly with 1 mg ofRNA-inactivated RSV strain long A, boosted with 0.25 mg of RSV after 2weeks, followed by 3 boosts with 50 μg of recombinant hRSV F_(TM)-NN(membrane anchorless form of the fusion protein, 70 kDa: Corral et al.2007; BMC Biotechnol. 7: 17) in a biweekly regimen. For allimmunizations the antigens were prepared as oil-PBS emulsions withStimune as adjuvant. Blood was collected from these animals 4 days and10 days after the fourth immunization, while also a Lymph node biopsywas taken 4 days after the fourth immunization. For the Nanocloneprocedure, 100 mL blood was collected 11 days after the final boost fromllamas 206 and 207.

Example 2 Library Construction

Peripheral blood mononuclear cells were prepared from blood samplesusing Ficoll-Hypaque according to the manufacturer's instructions. Next,total RNA was extracted from these cells as well as from the lymph nodebow cells and used as starting material for RT-PCR to amplify Nanobody®encoding gene fragments. These fragments were cloned into phagemidvector derived from pUC119 which contains the LacZ promoter, a coliphagepIII protein coding sequence, a resistance gene for ampicillin orcarbenicillin, a multicloning site and the gen3 leader sequence. Inframe with the Nanobody® coding sequence, the vector codes for aC-terminal c-myc tag and a (His)6 tag. Phage was prepared according tostandard methods and stored at 4° C. for further use, making phagelibraries 156, 157, 206, 207, 212 and 213.

Example 3 Nanobody® Selection with the F-Protein of hRSV

To identify Nanobodies® recognizing the fusion protein of RSV, libraries156, 157, 206, 207, 212 and 213 were used for selection on F_(TM)-NN(membrane anchorless form of the Long fusion protein, 70 kDa; Corral T.et al. 2007, BMC Biotechnol. 7: 17). The F_(TM)-protein (25 ng/well) wasimmobilized on Nunc Maxisorp ELISA plates. A control was included with 0μg/ml F_(TM)-. Bound phages were eluted from the F_(TM)-using trypsinand Synagis® (Palivizumab, MedImmune, humanized monoclonal antibody,described in Zhao and Sullender 2005, J. Virol. 79: 3962) in the firstand second round of selections. Remicade (Infliximab, anti-TNF;Centocor) was used as a control for Synagis®. A 100 molar excess ofSynagis® was used in order to identify Nanobodies® binding specificallyat the Synagis® binding site on RSV. Outputs from the first roundselections, eluted with Synagis® were used for second round selections.

In addition, selections were done using inactivated hRSV strain Long(Hytest #8RSV79). The F_(TM)-NN protein (25 ng/well) or RSV (5 to 50μg/well) was immobilized on Nunc Maxisorp ELISA plates, next to acontrol with 0 μg/ml antigen. Bound phages were eluted from theF_(TM)-NN using trypsin, Synagis® (Palivizumab, humanized monoclonalantibody, described in Zhao and Sullender 2005, J. Virol. 79: 396), or101F Fab (WO 06/050280, humanized monoclonal antibody) in the firstround of selection. Outputs from the first round selections eluted withSynagis® or 101F Fab were used for second round selections, using eitherNumax Fab (Motavizumab or MEDI-524, a third-generation humanizedmonoclonal antibody product evolved from palivizumab; WO 06/050166),Synagis® or 101F Fab for elution. Remicade (Infliximab, anti-TNF, seealso WO 09/068,625) was used as a control for Synagis®, while OmnitargFab (anti-Herz; in-house produced) served as control for Numax Fab and101F Fab. A 100 molar excess of Synagis®, Numax Fab or 101F Fab was usedin order to identify Nanobodies® binding specifically to antigenic sitesII or IV-VI epitopes on the RSV F-protein. To obtain Nanobodies®specific for the antigenic site IV-VI, second round selections wereperformed using two biotinylated peptides: at first, a peptidecomprising residues 422-436 of the F-protein (Long) (Abgent, San Diego,Calif.) encompassing the 101E binding epitope (Wu et al. 2007, J. Gen.Virol. 88: 2719-2723), secondly, a peptide mimic of the epitope of Mab19(HWSISKPQ-PEG4-K-biotin)(Chargelegue et al. 1998, J. Virol. 72:2040-2056).

Outputs of both rounds of selections were analyzed for enrichment factor(phage present in eluate relative to controls). Based on theseparameters the best selections were chosen for further analysis.Individual colonies were picked and grown in 96 deep well plates (1 mLvolume) and induced by adding IPTG for Nanobody® expression. Periplasmicextracts (volume: ^(˜)80 μl) were prepared according to standardmethods.

For testing of selected clones in RSV neutralization assays,periplasmatic extracts from 10 ml cultures were partially purified byusing IMAC PhyTips (Phynexus Inc, San Jose, Calif.). In here 800 μl ofperiplasmatic extracts was loaded onto PhyTips 200+ columns prepackedwith immobilized metal affinity chromatography resin, followed byelution of His-tagged Nanobodies® in 30 μl of 0.1M glycine-HCl/0.15MNaCl (pH3), after which eluates were neutralized with 5 μl of 0.5 MTris-HCl pH8.5.

Example 4 Nanobody® Selection with F_(TM)-NN of RSV Using NanocloneTechnology

Peripheral blood mononuclear cells (PBMCs) were prepared from bloodsamples using Ficoll-Hypaque according to the manufacturer'sinstructions. Antigen specific B-cells expressing heavy chain antibodieson their surface were isolated from the PBMCs via FACS sorting (for adescription of the Nanoclone technology reference is made to WO06/079372). Thereto, F_(TM)-NN protein was labeled with Alexa Fluor 488dye (Invitrogen, Carlsbad, Calif.; cat. nr. A20000) and subsequentlydesalted to remove residual non-conjugated Alexa Fluor 488 dye accordingto the manufacturer's instructions.

Pre-immune (background control) and immune PBMC of a llama were stainedwith fluorescent dye conjugated IgG1 (conventional heavy+light chainimmunoglobulins), IgG2- and IgG3 (heavy chain immunoglobulin classes)specific mouse monoclonal antibodies, fluorescently labeled DH59Bantibody (CD172a) (VMRD, Inc. Pullman, W A; Cat No. DH59B; Davis et al.1987, Vet. Immunol. Immunopathol. 15: 337-376) and Alexa 488 labeledantigen. TOPRO3 was included as a live/dead cell discriminator dye.IgG1+ B-lymphocytes, monocytes, neutrophils and dead cells were gatedout and therefore rejected from sorting. Antigen-specific (A488+) IgG2−or IgG3 positive B cells were single cell sorted individually intoseparate PCR plate wells containing RT-PCR buffer.

For llama 206, 1.9% antigen positive cells of the total amount ofIgG2/IgG3 positive living cells was obtained (1.0% in pre-immunereference sample), for llama 207 4.2% positive cells were obtained (0.7%in pre-immune reference sample). Heavy chain variable region genes wereamplified directly from these B-cells by single-cell RT-PCR and nestedPCR. PCR products were subsequently cloned into a TOPO-adaptedexpression vector derived from pUC119 which contained the LacZ promoter,a resistance gene for ampicillin or carbenicillin, a multicloning siteand the gen3 leader sequence. In frame with the Nanobody® codingsequence, the vector coded for a C-terminal c-myc tag and a (His)6 tag.The cloned constructs were transformed in TOP10 Escherichia coli cellsvia high throughput electroporation. Single clones were grown in 96 deepwell plates (1 ml volume) and induced by adding IPTG for Nanobody®expression. Periplasmic extracts (volume: ^(˜)80 μl) were prepared viaosmotic shock and analyzed for binding to F_(TM)-in a binding ELISA.

In short, 2 μg/ml of F_(TM)-was immobilized directly on Maxisorpmicrotiter plates (Nunc). Free binding sites were blocked using 4%Marvel in PBS. Next, 10 μl of periplasmic extract containing Nanobody®of the different clones in 100 μl 2% Marvel PBST were allowed to bind tothe immobilized antigen. After incubation and a wash step, Nanobody®binding was revealed using a rabbit-anti-VHH secondary antibody (for theperiplasmic fractions). After a wash step the Nanobodies® in theperiplasmic fractions were detected with a HRP-conjugatedgoat-anti-rabbit antibody. Binding specificity was determined based onOD values compared to controls having received no Nanobody®.

In total, 8 positive F_(TM)-NN binders (4 from llama 206, 4 from llama207) were obtained out of 52 cloned VHHs.

Example 5 Screening for Nanobodies® that Bind to Antigenic Site II orIV-VI

Periplasmic extracts containing single Nanobodies® were analyzed forbinding to the antigen site II or IV-VI, using an Alphascreen® assay(Perkin Elmer; Waltham, Mass.)(Garcia-Barreno at al. 1989, J. Virol. 63:925-932; Lopeze at al. 1998, J. Virol. 72: 6922-6928). In this setupF_(TM)-NN is bound simultaneously by Fabs of Synagis® and 101F, allowingdetection of Nanobodies® that interfere with binding of each of therespective antigenic sites II and IV-VI. In here, periplasmic extractswere added to F_(TM)-NN protein (0.3 nM) and incubated for 15 minutes.Subsequently biotinylated Fab Synagis® (0.3 nM) and Fab 101F conjugatedacceptor beads (10 μg/ml) were added and this mixture was incubated for1 hour. Finally streptavidin-coated donor beads (10 μg/ml) were addedand after 1 hour incubation the plate was read on the Envisionmicroplate reader. Periplasmic extracts were diluted 25-fold whichcorresponds roughly to a final concentration of 40 nM. The assay wasvalidated by titration of the known competitors of Synagis®, mabs 18B2(Argene, Varilhes, France; 18042 N1902) and 2F7 (Abcam, Cambridge, UK;ab43812). Also Synagis® Fab, Numax Fab, and 101F Fab were analyzed, withNumax Fab having the lowest IC50 value (8.6 E-11 M) followed by Synagis®Fab (5.97 E-10 M) and 101F Fab (1.12 E-9 M). For the screening ofperiplasmatic extracts (at 1/25 dilution) both Numax Fab (40 nM) and101F Fab (40 nM) were used as positive controls, while irrelevantperiplasmatic extracts served as negative controls. Clones thatinterfered with binding to F_(TM)-NN protein in the Alphascreen® morethan 75% relative to the negative controls were identified as hit. Intotal 341 hits were identified out of 1856 clones, derived from all 6llamas but the majority coming from llamas 206 and 207. In addition, outof 8 clones obtained from Nanoclone selections 3 clones showedcompetition.

The correct antigen site (II or IV-VI) of the competitors wasdeconvoluted by means of a competition ELISA with biotinylated Synagis®Fab (2 nM) or biotinylated 101F Fab (3 nM) for binding to F_(TM)-NNprotein (1 μg/ml). In short, the F_(TM)-NN protein was immobilized onMaxisorp microtiter plates (Nunc) and free binding sites were blockedusing 4% Marvel in PBS. Periplasmatic extracts were diluted 1/10 andmixed with the biotinylated Fab prior to binding to the immobilizedF_(TM)-NN protein. Control periplasmic fractions selected against otherviral coat proteins were included. The competing antibody was allowed tobind to the immobilized antigen with or without Nanobody®. Afterincubation and a wash step, detection occurred via Extravidin-HRPconjugated secondary antibodies (Sigma-Aldrich, St. Louis, Mo.; Cat. No.E2886). Binding specificity was determined based on OD values comparedto controls having received no Nanobody®.

All hits were subjected to sequence analysis and classified intofamilies according to their CDR3 sequences (see Table C-4 and A-1 in PCTapplication PCT/EP2009/056975 entitled “Amino acid sequences directedagainst envelope proteins of a virus and polypeptides comprising thesame for the treatment of viral diseases” filed by Ablynx N. V on 5 Jun.2009).

Example 6 Screening for RSV Neutralizing Nanobodies®

From all six hRSV libraries 163 unique sequences (160 identified fromphage libraries, 3 derived from Nanoclone) were analyzed for RSV Longneutralizing capacity in a micro-neutralization assay as partiallypurified proteins. Hep2 cells were seeded at a concentration of 1.5×10⁴cells/well into 96-well plates in DMEM medium containing 10% fetal calfserum (FCS) supplemented with Penicillin and Streptomycin (100 U/ml and100 μg/ml, respectively) and incubated for 24 hours at 37° C. in a 5%CO₂ atmosphere. The virus stock used is referred to as hRSV strain long,Long LM-2 and Long M2 (used interchangeably) and is a virus stockderived from ATCC VR-26 of which the sequence of the F proteincorresponds to P12568 or M22643. The virus stock has been passagedseveral times from the ATCC stock. The sequence of the F-protein wasconfirmed to be identical to P12568 (see example 9). A standard quantityof hRSV strain Long LM-2 was pre-incubated with serial dilutions of afixed volume of Phytips purified Nanobodies® (20 μl) in a total volumeof 50 μl for 30 minutes at 37° C. The medium of the Hep2 cells wasreplaced with the premix to allow infection for 2 hours, after which 0.1ml of assay medium was added. The assay was performed in DMEM mediumsupplemented with 2.5% fetal calf serum and Penicillin and Streptomycin(100 U/ml and 100 μg/ml, respectively). Cells were incubated for anadditional 72 hours at 37° C. in a 5% CO2 atmosphere, after which cellswere washed twice with 0.05% Tween-20 in PBS and once with PBS alone,after which the cells were fixed with 80% cold acetone (Sigma-Aldrich,St. Louis, Mo.) in PBS (100 μl/well) for 20 minutes at 4° C. and left todry completely. Next the presence of the F-protein on the cell surfacewas detected in an ELISA type assay. Thereto, fixed Hep2 cells wereblocked with 2% Bovine Serum Albumin (BSA) solution in PBS for 1 hour atroom temperature, than incubated for 1 hour with Synagis® (2 μg/ml). Fordetection goat Anti-Human IgG, Fcγ fragment specific-HRP (JacksonImmunoResearch, West Grove, Pa.) was used, after which the ELISA wasdeveloped according to standard procedures.

In addition to the previously identified RSV neutralizing Nanobodies®191D3 (SEQ ID NO: 9) and 192C4 (SEQ ID NO: 11), which were included aspositive controls in the screening, 5 antigenic site II clones showedstrong RSV Long neutralizing activity: 1E4 (also referred to as 207D1;SEQ ID NO: 1), 7B2 (SEQ ID NO: 2), NC23 (SEQ ID NO: 3), and two membersof the same family 15H8 (SEQ ID NO: 4) and NC41 (SEQ ID NO: 5) (TableA-1). None of the antigenic site IV-VI specific Nanobodies® showed morethan very weak neutralizing activity for hRSV Long LM-2 strain.

Example 7 Production of hRSV Nanobodies®

In addition to the previously identified RSV neutralizing Nanobodies®191D3 (SEQ ID NO: 9) and 191E4 (SEQ ID NO: 10), which were included aspositive controls in the screening, five new neutralizing Nanobodies®selected from the screening described above (1E4, 7B2, 15H8, NC23 andNC41) as well as 1 antigenic site IV-VI Nanobodies® (15B3; SEQ ID ND: 7)were expressed, purified and further characterised. Thereto the encodingsequences were recloned in an expression vector derived from pUC119which contained the LacZ promoter, a resistance gene for kanamycin, amulticloning site and the OmpA signal peptide sequence. In frame withthe Nanobody® coding sequence, the vector coded for a C-terminal c-myctag and a (His)6 tag.

Expression occurred in E. coli TG-1 cells as c-myc, His6-tagged proteinsin a culture volume of 1 L. Expression was induced by addition of 1 mMIPTG and allowed to continue for 3 hours at 37° C. After spinning thecell cultures, periplasmic extracts were prepared by freeze-thawing thepellets and resuspension in dPBS. These extracts were used as startingmaterial for immobilized metal affinity chromatography (IMAC) usingHistrap FF crude columns (GE healthcare, Uppsala, Sweden). Nanobodies®were eluted from the column with 250 mM imidazole and subsequentlydesalted towards dPBS.

Example 8 Characterization of hRSV Nanobodies®

Binding to F-Protein in ELISA

All purified Nanobodies® were shown to bind to the F-protein in abinding ELISA to F_(TM)-NN protein and to hRSV. Results for hRSV bindingare shown in Table B-1. In short, 1 μg/ml of F_(TM)-NN or 5 μg/ml hRSV(Hytest Turku, Finland) were immobilized directly on Maxisorp microtiterplates. Free binding sites were blocked with 1% casein. Serial dilutionsof purified Nanobodies® were allowed to bind the antigen for 1 hour.Nanobody® binding was revealed using a rabbit-anti-VEIN secondaryantibody, and final detection with a HRP-conjugated goat-anti-rabbitantibody. Binding specificity was determined based on OD values comparedto irrelevant Nanobody® controls.

Binding to F-Protein in Biacore

To determine the precise binding affinities of the purified Nanobodies®,a kinetic analysis was performed using Surface Plasmon resonanceanalysis on the F_(TM)-NN protein. For preincubation of the SensorchipCM5, 10 μg/ml hRSV F_(TM)-protein was left on for 120 seconds. Forimmobilization by amine coupling, EDC/NHS was used for activation andethanolamine HCl for deactivation (Biacore, amine coupling kit). 100 nMSynagis® was added and then 100 nM of the Nanobodies®. Evaluation of theoff-rates was performed by fitting a 1:1 interaction model (Langmuirbinding model) by Biacore T100 software v1.1. The off-rates and affinityconstants are shown in Table B-1.

Competition with Synagis®

The ability of purified Nanobodies® to compete with Synagis® Mab orbiotinylated Synagis® Fab for binding to F_(TM)-NN was determined incompetition ELISA following the procedure as essentially described inexample 5. FIG. 1 shows a representative example of a competition ELISAwherein purified Nanobodies® compete with biotinylated Synagis® Fab forbinding to F_(TM)-NN. EC50 values are summarized in Table B-1.

Example 9 In Vitro Micro Neutralization of Distinct hRSV Strains

The potency of purified Nanobodies® in neutralization of different typeA and B RSV strains was tested by the in vitro micro neutralizationassay (see Example 6). Viral stocks of RSV Long LM-2 (Accession No.P12568; ATCC VR-26), RSV A-2 (ATCC VR-1540; lot nr. 3199840) and RSV B-1(ATCC VR-1580; lot nr. 5271356) were prepared into Hep2 cells andsubsequently titrated to determine the optimal infectious dose for usein the micro neutralization assay. Results of neutralization potenciesof the different purified Nanobodies® are shown in Table B-1. While allsix Nanobodies® that recognize the Synagis® epitope could efficientlyneutralize type A strains Long and A-2, they failed to neutralizeinfection with the B-1 strain or did so at concentrations >1 μM. The101F competitors 15B3 and 191E4 showed very weak neutralization potencyon the B-1 strain only when administrated at μM concentrations.

The sequences of the respective F-proteins of the different RSV strainswere verified by means of reverse-transcriptase PCR and subsequentsequence analysis. Briefly, total RNA was isolated from RSV-infectedHep2 cells using RNeasy mini kit (Qiagen, Venlo, Netherlands), afterwhich complementary DNA was prepared using Superscript III reversetranscriptase kit (Invitrogen, Carlsbad, Calif.). The F-protein of RSV Astrains was amplified and sequenced using the primers described inKimura et al. 2004 (Antiviral Research 61: 165-171). For amplificationof the RSV B-1 strain F-protein the following primers were used:FB1_outer_for: cttagcagaaaaccgtga (SEQ ID NO: 13); FB1_outer_rev:tgggttgatttgggattg (SEQ ID NO: 14); FB1_seq_(—)1123-for:ggactgatagaggatggta (SEQ ID NO: 15); FB1_seq_(—)1526-rev:gctgacttcacttggtaa (SEQ ID NO: 16). The sequence of RSV B-1 straincorresponded to Accession nr P13843, with an additional point mutationSer540Leu. The sequence for the RSV Long M2 strain correspondedcompletely to the reported sequence (Accession nr M22643). The sequencefor the strain RSV A-2 corresponded to Accession M11486. See also TableA-2.

Example 10 Construction, Production and Characterization of MultivalenthRSV Nanobodies®

Multivalent Nanobody® constructs connected by Gly-Ser linkers ofdifferent lengths and composition were generated by means of separatePCR reactions (1 for the N-terminal, 1 for the middle (in case oftrivalent) and 1 for the C-terminal Nanobody® subunit) using differentsets of primers encompassing specific restriction sites. Similarly,multivalent constructs connected by Ala-Ala-Ala linker were generated.All constructs were cloned into an expression vector derived from pUC119which contained the LacZ promoter, a resistance gene for kanamycin, amulticloning site and the OmpA signal peptide sequence. In frame withthe Nanobody® coding sequence, the vector coded for a C-terminal c-myctag and a (His)6 tag. In case a 35 Gly-Ser-linker was present in themultivalent construct, an expression vector was used derived from pUC119which contained the LacZ promoter, a resistance gene for kanamycin andthe OmpA signal peptide sequence. Directly downstream of the signalpeptide a multiple cloning site was present for Nanobody® insertion,followed by a 35Gly-Ser linker encoding DNA sequence and a secondmultiple cloning site for cloning of a second Nanobody® sequence. Inframe with the resulting Nanobody®-35Gly-Ser-Nanobody® coding sequence,the vector coded for a C-terminal c-myc tag and a (His)6 tag. Table B-2lists the multivalent constructs generated with RSV-specificNanobodies®. The sequences of the multivalent constructs are shown inTable A-3.

Multivalent RSV Nanobody® constructs were expressed, purified andfurther characterized. Production was done in E. coli TG1 cells,followed by purification from the periplasmic fraction via the His-tagby IMAC and desalting, essentially as described in Example 7. Forcertain trivalent constructs (e.g. RSV401, RSV404, RSV406) productionwas done in P. pastoris followed by purification from the mediumfraction. All trivalent Nanobodies® were subjected to gel filtration asa final step to remove possible bivalent and monovalent degradationproducts.

Binding of purified multivalent Nanobodies® to the hRSV F-protein wasconfirmed in ELISA on both F_(TM)-protein and on hRSV (see Example 8).For the majority of Nanobodies® the formatting into bivalent andtrivalent constructs resulted in a clear but limited (up to 10-foldincrease) avidity effect, with the exception of multivalents of 7B2 andNC23 which showed similar EC50 values as their monovalent counterparts(as shown for 7B2 in FIG. 2).

Example 11 Potency of Bi- and Trivalent Constructs to Neutralize hRSV

The potency of the Nanobody® constructs was evaluated in the RSVneutralization assay on different RSV strains (see examples 6 and 9).Bivalent Nanobodies® binding antigenic site II showed marked increasesin potencies of 100- to 1000-fold (i.e. much higher than the increase inaffinity) in neutralization of Long relative to their monovalentcounterparts, with IC50 values ranging from 50-380 pM, being better orsimilar to Numax Fab. On the RSV B-1 strains however, the potencyincrease was much less strong, and none of the dimeric constructs wasmore potent than Synagis®. Surprisingly, this could be overcome by thegeneration of trivalent constructs, as shown in FIG. 3. Trivalentconstructs with three Nanobodies® binding antigenic site II were atleast 1000-fold more potent neutralizers on RSV B-1 strains than theirmonovalent counterparts.

Example 12 Reactivity of Monovalent Nanobodies® with Escape Mutants ofthe Long Strain

A number of escape mutants, described in Lopez et al. 1998 (J. Virol.72: 6922-6928), and specific for antigenic site II (R47F/4, R47F/7,RAK13/4, R7C2/11, R7C2/1) or IV-VI (R7.936/1, R7.936/4, R7.936/6,R7.432/1) or the combination of both (RRA3), were selected for testingtheir reactivity with 10 monovalent Nanobodies®, including Nanobody®19107 (SEQ ID NO: 8) previously identified as not binding to antigenicsites II or IV-VI.

This assay was performed according to Lopez et al. 1998 (J. Virol. 72:6922-6928). In brief, each Nanobody® was tested at 0.2 μg/ml in ELISAusing antigen extracts of HEp-2 cells infected with the different escapemutants. Absorbance results were normalized for reactivity on thereference virus strain (Long wild type) strain as well as on the controlNanobody® 191C7. Results are shown in Table B-3.

A reactivity of >75% is indicated as a filled black square, dark hatchedsquares correspond to a reactivity between 75 and 50%, light hatchedsquares correspond to a reactivity of 25-50% and less than 25%reactivity is indicated by a blank square. In general Nanobodies®already identified as antigenic site II binders previously (192C4,191D3, 191F2, NC23, 15H8, 7B2 and NC41) were found to be sensitive totypical mutations in antigenic site II, while the other Nanobodies®already identified as antigenic site IV-VI binders were indeed sensitivefor mutations in these sites.

Example 13 Reactivity of Multivalent Nanobodies® with Escape Mutants ofthe Long Strain

Subsequently a number of multivalent constructs was analyzed on alimited panel of escape viruses to assess binding. This assay wasperformed according to Lopez et al. 1998 (J. Virol. 72: 6922-6928). Inbrief, each Nanobody® was tested at 0.1 μg/ml for monovalent Nanobodies®and at 0.05 μg/ml for bi- and trivalent Nanobodies® in ELISA usingantigen extracts of HEp-2 cells infected with the different escapemutants. Absorbance results were normalized for reactivity on thereference virus strain (Long wild type) strain as well as on the controlNanobody® (191E4; SEQ ID NO: 10, in this particular assay). Results areshown in Table B-4.

A reactivity of >75% is indicated as a filled black square, dark hatchedsquares correspond to a reactivity between 75 and 50%, light hatchedsquares correspond to a reactivity of 25-50% and less than 25%reactivity is indicated by a blank square. Remarkably, multivalentconstructs showed improved binding compared to their monovalentcounterpart, to the mutant virus R7C2/11. In addition the biparatopicconstruct RSV403 was not sensitive to any of the mutants.

Example 14 Neutralization of Escape Mutants of the Long Strain byMultivalent Nanobodies®

In examples 12 and 13, the binding of monovalent Nanobodies® to typicalantigenic site it and/or IV-VI RSV escape mutants has been described.Binding of Nanobodies® specifically recognizing these antigenic siteswas almost lost or significantly reduced. Formatting of theseNanobodies® into bi- or trivalent constructs partially restored bindingactivity but not for all three escape mutant viruses. Binding to theescape mutant R7C2/1 (mutation K272E in antigenic site II) remainedbelow the level of 25% for any bi- or trivalent construct consistingsolely of antigenic site II binding Nanobodies®. The Nanobodies® 15B3and 191E4, which are binding to antigenic site IV-VI, were the onlyNanobodies® (as such or in biparatopic constructs) able to bind thismutant at a level of 75% or more.

More detailed analysis of the data indicated that binding towards R7C2/1slightly increased when the valency of the Nanobody® was increased. Thebinding of 7B2 constructs was 0, 4.4 and 13% respectively for themonovalent, bivalent (RSV106) and trivalent (RSV400) formats. Such a lowlevel of residual binding is expected to result in very high loss ofpotency to neutralize RSV.

The neutralizing potency of Nanobodies® was assessed on the sameselected set of escape mutants as described in example 13. For thispurpose the monovalent Nanobodies® 7B2, 15H8 and NC41 were compared totheir respective trivalent counterparts, RSV400, RSV 404 and RSV 407. Ofnote, in example 13 only RSV400 was assessed for binding these escapemutants. In addition also the biparatopic trivalent molecule RSV403(7B2-15B3-7B2) was analyzed for its neutralizing capacity.

The hRSV micro neutralization assay was essentially performed asdescribed in example 6. In brief, Hep2 cells were seeded at aconcentration of 1.5×10⁴ cells/well into 96-well plates in DMEM mediumcontaining 10% fetal calf serum (FCS) supplemented with Penicillin andStreptomycin (100 U/ml and 100 μg/ml, respectively) and incubated for 24hours at 37° C. in a 5% CO₂ atmosphere. Viral stocks of differentviruses were prepared into Hep2 cells and subsequently titrated todetermine the optimal infectious dose for use in the microneutralization assay. A standard quantity of the specific hRSV strainwas pre-incubated with serial dilutions of purified Nanobodies® in atotal volume of 50 μl for 30 minutes at 37° C. The medium of the Hep2cells was replaced with the premix to allow infection for 2 hours, afterwhich 0.1 ml of assay medium was added. The assay was performed in DMEMmedium supplemented with 2.5% fetal calf serum and Penicillin andStreptomycin (100 U/ml and 100 μg/ml, respectively). Cells wereincubated for an additional 72 hours at 37° C. in a 5% CO2 atmosphere,after which cells were washed twice with 0.05% Tween-20 in PBS and oncewith PBS alone, after which the cells were fixed with 80% cold acetone(Sigma-Aldrich, St. Louis, Mo.) in PBS (100 μl/well) for 20 minutes at4° C. and left to dry completely. Next the presence of the F-protein onthe cell surface was detected in an ELISA type assay. Thereto, fixedHep2 cells were blocked with 5% Porcine Serum Albumin solution in PBSfor 1 hour at room temperature, than incubated for 1 hour withanti-F-protein polyclonal rabbit serum (Corral et al. 2007, BMCBiotechnol, 7: 17) or Synagis® (2 μg/ml). For detection goatAnti-rabbit-HRP conjugated antibodies or goat Anti-Human IgG, Fcγfragment specific-HRP (Jackson ImmunoResearch, West Grove, Pa.) wasused, after which the ELISA was developed according to standardprocedures.

As shown in FIGS. 4A-C, the monovalent Nanobodies® had almost noneutralizing potential towards the antigenic site II escape mutantviruses R7C2/11 and R7C2/1. The potency to neutralize the R7.936/4antigenic site IV-VI variant was comparable to the potency to neutralizethe wild type Long strain. These data are in line with the binding dataof example 12 and the epitope mapping as described for these Nanobodies®in example 5.

The trivalent Nanobody® constructs however, were potently neutralizingall 3 escape mutants (FIGS. 4D-G). Maximal inhibition was observed atconcentrations as low as about 20 nM while this level of inhibition wasnot observed for the monovalent Nanobodies® at concentrations up to 2μM. The potent neutralization of R7C2/1, almost equivalent to theneutralization of R7C2/11, is most surprising since example 13 showed avery significant loss of binding activity for the trivalent moleculeRSV400 which was expected to result in a very high loss ofneutralization potency. The bivalent IgG Synagis® Palivizumab, alsorecognizing antigenic site II was not able to block replication ofR7C2/1 or R7C2/11 significantly at concentrations of about 0.2 μM. Atthis concentration an IC50 was not reached while R7.936/4 and wild typeLong virus were neutralized with an IC50 of a few nM (data not shown).

Example 15 Analysis of Impact of Linker Length on Potency of NC41Trivalents

To determine the impact of the linker length of trivalents of NC41,different constructs with linkers ranging from 3Ala, 9GS, 15GS, to 20GSlinkers (RSV408, RSV409, RSV407 and RSV410 resp.) were generated. Allfour NC41 trivalents were able to completely neutralize both RSV B-1 andLong strains (FIG. 5). No effect of linker length was observed inneutralization of RSV Long, as all constructs were equally potent. Bycontrast, the constructs with 9GS and 3Ala linkers had increased IC50values on the B-1 strain, indicating that a minimal linker length of15GS is required for maximal potency. This may be explained by theobservation that bivalent NC41 constructs already are very potentneutralizers on Long, while on the B-1 strain the potency differencebetween bivalent and trivalent NC41 is much larger (see Example 11). InRSV408 and RSV409 the accessibility of the middle Nanobody® may be lessoptimal.

Example 16 Humanization of Nanobody® NC41

The sequence of Nanobody® NC41 was aligned to the human germline VH3-23to allow selection of residues suitable for further humanization of theNanobody® sequence. In addition, in silico analysis was done to identifyresidues that are potentially prone to post-translational modifications,such as Asp isomerisation, and to identify mutations that might improvethe chemical stability. The CDR regions and the so-called Hallmarkresidues, which are known to be essential for the stability and potencyof Nanobodies® were excluded for modification.

For NC41 in total 11 positions were selected for mutation to thecorresponding human residue: Four mutations were simultaneous introduced(Val5Leu, Ala14Pro, Glu44Gly, Gln108Leu), as these residues were notexpected to dramatically affect the Nanobody® function (based on datafrom other Nanobodies®). In this basic variant, seven residues of whichit was unknown whether mutation to the human counterpart was allowed(Ser19Arg, Ile20leu, Ala74Ser, Gly78Leu, Ala83Arg, Asp85Glu, Arg105Gln)were mutated using a library approach, allowing either the wildtype orthe corresponding human amino acid at each position. The resultinglibrary, with a theoretical diversity of 128, was generated by geneassembly using overlapping oligonucleotide sequences containingdegenerated codon use, and subsequently cloned into an expression vectorderived from pUC119 which contained the LacZ promoter, a resistance genefor kanamycin, a multicloning site and the OmpA leader sequence. Inframe with the Nanobody® coding sequence, the vector coded for aC-terminal c-myc tag and a (His)6 tag. Nanobodies® were produced in theperiplasm of E. coli (see Example 7). Library diversity was confirmed bysequence analysis.

Periplasmic extracts from 368 individual NC41 variants and wildtype NC41were generated and subjected to a functional screening cascade toidentify the best humanized NC41 variant, in terms of both potency andstability. In a first step, RSV binding of humanized NC41 variants toRSV Long was determined in ELISA (Hytest, Turku Finland; #8RSV79)(seeExample 8).

Moreover, the positive binders were analyzed for binding to Hep2 cellsinfected with RSV B-1 strain. In here, Hep2 cells were seeded into96-wells plates and infected with RSV B-1 strain, essentially followingthe procedure described for the neutralization assay (see Example 6).Three days later cells were fixed with ice-cold acetone and plates wereused in an ELISA assay using periplasmic extracts at differentdilutions. Nanobody® binding to Hep2-B1 infected cells was detectedusing anti-VHH rabbit polyclonal antibody, followed by goatAnti-rabbit-HRP conjugated antibodies, after which the ELISA wasdeveloped according to standard procedures.

Additionally, in order to verify if the introduced mutations affectedthe temperature stability, periplasmatic extracts of all binders wereheated to 74° C. for 2 hours, which is 5° C. above the meltingtemperature of wildtype NC41. The binding to RSV long before and afterheating was analyzed in ELISA, and the ratio of binding signal after vs.before heating was taken as measure for temperature stability.

Finally, the kinetic off-rates of the variants were determined inBiacore assay on the F_(tm)-NN protein, as described in Example 8.

All binders were sequenced and ranked according to their capacity tobind the F-protein of RSV. When analyzing the sequences of the strongestbinders, a clear preference for Gln105 (human residue) was observed inall cases. Whereas the Ile20Leu mutation appeared underrepresented, forall other positions there was no clear preference for either the wildtype or the human sequence, with variants containing up to 10 mutationscompared to wildtype NC41. Notably, in one variant an additionalpointmutation (Gly54Asp) within the CDR2 region was observed. Thisvariant, NC41 variant 6, showed the lowest off-rate of all variants andwildtype NC41, resulting in affinity increase.

Based on the sequence and functional data, 18 variants (Table A-4) wereselected for further characterization as purified proteins (FIGS. 6 and7). All variants were produced and purified, and potencies forneutralization of RSV Long and B-1 were determined in the microneutralizations assay. While most variants showed very similar activityto wildtype NC41, several variants showed increased potency on both Long(2-fold) and B-1 (6-fold), with the strongest neutralizers being NC41variants 6, 8, 9 17, and 18. Notably, variant 18 was maximally humanizedat all 11 positions, with the additional introduction of Asp54 in theCDR2 region. Variant 10 and 11 were more potent in neutralizing B-1strain than NC41, but not on Long strain.

For a select panel of NC41 variants the kinetic binding parameters weredetermined in Biacore on F_(tm). NN protein (Table B-5) as described inExample 8. No significant differences in the calculated data wereobserved for NC41 and the humanized NC41 variants 6, 8 and 17. It shouldbe noted that the on-rates of all NC41 variants were at the detectionlimit of the instrument, but the off-rates could be ranked asv06<v17<NC41<v08. The impact of the Gly to Asp mutation in CDR2(position 54) could be clearly demonstrated when comparing v17 and v18as this is the only difference in these maximally humanized variants.Neutralization was tested for both the Long strain and the B-1 strain intwo independent assays in comparison to the NC41 wild type as shown intable B-5. In both assays NC41v18 was more potent than NC41 on bothviruses and in both assays NC41v18 was more potent than NC41v17 on theLong strain. The improved neutralization of NC41v18 was also observedfor the B-1 strain in the second assay.

All NC41 variants were subjected to heat-induced unfolding to assess theeffect of the introduced mutations on the stability of the protein.Thereto the melting temperature (Tm) was determined by stepwise increasein temperature in presence of Sypro Orange, a dye that binds to Trpresidues that become exposed upon unfolding of the protein. All variantsshowed to have increased Tm relative to wildtype NC41 (69° C.), up to 9°C. for variant 18.

Example 17 Further Sequence Optimization of NC41 for Expression

The sequence of Nanobody® NC41 was further analyzed with the aim tooptimise expression in Pichia pastoris. NC41 variants 19-26 weredesigned by combining humanized positions that were shown to bepermitted without loss in potency in the micro-neutralization assay(Example 16). Four mutations were simultaneous introduced (Ala14Pro,Ser19Arg, Ile20Leu, Gln108Leu), while three mutations were bothindividually and in each possible combination examined (Ala83Arg,Asp85Glu, Arg105Gln)(see Table A-4). All constructs were cloned into anexpression vector and introduced into the Pichia pastoris strain XL-33,after which the number of incorporations in the Pichia genome wasassessed by quantitative real-time PCR. From each construct one clonewith 1-2 copies and one with four or more copies were selected for smallscale productions, and expression yield of NC41 variants relative towild type was estimated by gel electrophoresis on SDS-PAGE gels. NC41variants 20, 22, 24, 25 and 26 showed the highest expression, withsimilar expression levels as wild type NC41 already at low copy number.

NC41 variants 22 and 26 were recloned in an expression vector for E.coli for production and purification of Myc-His-tagged Nanobodies (seeexample 7). The potency of both variants for neutralization of RSV Longwas tested in the micro neutralization assay, as described in example 6.Both variants were equally potent as wild type NC41 (IC50 of 126 and 310nM for v22 and v26, respectively).

Example 18 Sequence Optimization of RSV407 for Chemical Stability

During the production of the Nanobodies and polypeptides of theinvention, pyro glutamate (pGlu) on the amino terminus was observed (viaRP-HPLC). Levels of more than 15% pGlu were detected followingfermentation and the level of pGlu was steadily increasing upon storageduring stability studies. Therefore, the N-terminal Glutamate (E) waschanged into an Aspartate (D). This would eliminate the possibility ofpGlu post-translational modification of the N-terminus and hence lead toincreased product stability.

The amino acid sequence of the sequence optimized Nanobody® variant isgiven in Table A-5 (RSV434; SEQ ID NO: 142) respectively. For theproduction of this Nanobody® a Pichia expression system was developedbased on the commercially available system from Invitrogen using X-33 asa host strain. The system makes use of the AOX1 promoter to drive theproduction of the Nanobody® and uses the alpha mating secretion peptidefor secretion of the Nanobody® into the medium.

The sequence optimized RSV434 was analyzed for expression levels, viaRP-HPLC, SE-HPLC and compared to the parental molecule (RSV407) withrespect to RSV neutralization.

There was no significant difference in expression level compared toRSV407 and both the low and high copy number clones were producing morethan 1 g/L clarified medium (cell free).

One ml samples were captured on a 1 ml MEP Hypercel column, eluted andanalyzed via SE-HPLC and RP-HPLC. SE-HPLC analysis showed monomericmaterial, whereas RP-HPLC analysis, as expected, clearly showed theabsence of the pGlu post peak.

RSV434 was further purified from the medium, captured on MEP HyperCelland polished via anion exchange chromatography.

Rn hRSV micro neutralization assay was essentially performed asdescribed in example 6. FIG. 9 shows the neutralization on both RSV Longand B-1 strains by both RSV407 and its sequence optimized variantRSV434.

Example 19 Preparation of Multivalent Constructs of Humanized and/orSequence Optimized NC41 Nanobody®

NC41 humanized variants of Example 16 were formatted as trivalentconstructs using 15GS linkers (sequences are shown in Table A-5). Thetrivalents were produced and purified as described in Example 10. FIG.8A shows the neutralization on both RSV Long and B-1 strains of two ofthe trivalent humanized NC41 variants with their correspondingmonovalent Nanobodies®. FIG. 8B shows the neutralization on both RSVLong and B-1 strains of the trivalent NC41 variants. IC50 values forneutralization of RSV Long and B-1 strains by the trivalent NC41variants are shown in Table B-7. Similar as to parental NC41 trivalent(RSV407), trivalents of the humanized NC41 variants were around 60 timesmore potent neutralizers of Long than Synagis®. On the B-1 straintrivalents were more potent neutralizers than Synagis, but here alsoslightly enhanced compared to the trivalent of parental NC41 RSV407 infollowing order RSV427>RSV426>RSV414. The increased potency ofmonovalent variants for B-1 thus appeared to have resulted in slightlyimproved trivalents.

Based on further sequence optimization shown in Examples 17 and 18, anumber of additional trivalent constructs (Table B-6) were generated.All constructs were cloned in a Pichia pastoris expression vector,transformed into Pichia and subjected to fermentation to test expressionlevels, stability and potency. Both in small scale shake flaskexpressions and fermentation RSV440 (variant 26) and RSV441 (variant 22)showed high expression levels.

Example 20 In Vitro Efficacy of the Multivalent Constructs

The neutralizing capacity of Nanobody RSV434 and Synagis was evaluatedin a plaque reduction assay against 31 RSV/A and 30 RSV/B clinicalisolates. Both anti-RSV compounds as well as Synagis were tested at asingle concentration of 40 μg/ml.

Synagis and RSV434 both performed efficiently with respectively 87% and97% of the strains being reduced in virus titers by at least 100-foldcompared to PBS control (Table B-8). In addition, RSV434 showed greaterneutralizing capacity compared to Synagis. The majority of the RSVstrains (84%) were completely inhibited by RSV434 while significantlyfewer strains (20%) were completely inhibited by Synagis (Table B-8).

Example 21 In Vivo Efficacy of the Multivalent Constructs

The cotton rat model is the golden standard model for RSV. In thismodel, the cotton rats are infected with the RSV/Tracy strain (day 0)and 4 days after infection, viral titers and viral RNA are assessed inlung lavages and nasal washes. In a prophylactic set-up, a significantand dose-dependent decrease in viral load was observed upon intranasaladministration of RSV407, 24 hours before RSV infection (FIG. 10).

In addition, a therapeutic approach was explored in which infectedcotton rats were treated with the Nanobodies, including RSV434, after 24h or 48 h of infection thereby mimicking the situation of RSV infectedhumans, in both cases significant inhibition of viral replication wasobserved (Table B-9 and FIG. 11).

In all studies performed to date, the Nanobody was deliveredintranasally as a mimic for pulmonary delivery. Using this route ofadministration 9-41% of Nanobody was available in the lungs as assessedby ELISA on bronchial lavage taken shortly after administration.

In an attempt to overcome the possible interference of residual Nanobodyin the lung lavages, the viral detection was delayed to day 7 postinoculation. A separate pharmacokinetic study performed in SpragueDawley rats allowed to estimate the half life of the Nanobody in thelung to be about 10.8. At day 7 which is 5-6 days after the lastadministration, the Nanobody is sufficiently cleared from the lung to nolonger interfere in the assay. The viral load of positive controlanimals dropped from 10E5 to 10E2 pfu/ml. Nevertheless it was stillpossible to show a reduction of about 0.6 log by treatment with RSV407(Table B-9).

As an alternative approach a quantitative PCR was developed to detectviral RNA. Both in prophylactic and therapeutic experiments asignificant reduction in RSV RNA was observed (Table B-9).

Example 22 Generation of RSV Escape Mutants

In order to identify the critical contact residues with the F-protein,the generation of RSV Long escape mutants was analyzed after culturingRSV Long in presence of Nanobodies at about their respective IC90concentrations. Both monovalent NC41 (at 5 μg/ml) and its trivalentRSV407 (at 2.5 ng/ml) were used, as well as the bispecific trivalentRSV413 (NC41-15B3-NC41) to verify if a construct that recognizes twodifferent epitopes would affect the time frame of viral escape onset.After 12 passages of successive incubation of Long on Hep2 cells inpresence of Nanobodies, viral out growth was observed for the conditionswith monovalent NC41 but surprisingly not with the trivalent Nanobodies.Single virus stocks were purified from plaques for repetitive rounds,after which the sequence of the F-protein of the potential escapevariant could be determined. Two distinct escape variants wereidentified for NC41, NC41/13 with the mutation of N262Y, and NC41/17containing mutation N276Y.

Tables

TABLE A-1 Sequences of monovalent Nanobodies ® that bind RSV F proteinSEQ ID Nanobody ® NO: Sequence 1E4  1EVQLVESGGGLVQAGGSLRLSCEASGRTFSSYGMGWERQAPGKEREF 207D1VAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNPGAYYYTWAYDYWGQGTQVTVSS 7B2  2EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSS NC23  3EVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSFIYDWAYDHWGQGTQVTVSS 15H8  4EVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWERQAPGKEREF 19C4VAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS NC41  5EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS NC39  6EVQLVESGGGWVQAGGSLRLSCAASGRAFSSYAMGWIRQAPGKEREFVAGIDQSGESTAYGASASGRFIISRDNAKNTVHLLMNSLQSDDTAVYYCVADGVLATTLNWDYWGQGTQVTVSS 15B3  7EVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSS 191C7  8EVQLVESGGGLVQAGGSLRLSCAASGSSGVINAMAWHRQAPGKERELVAHISSGGSTYYGDFVKGRFTISRDNAKDTVYLQMNSLKPEDTAVYY CHVPWMDYNRRDYWGQGTQVTVSS191D3  9 EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREF 1G3VAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSS 191E4 10EVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREF 1B2VATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSS 192C4 11EVQLVESGGGLVQAGGSLRLSCEASGRTFSSYAMVGWFRQAPGKEREFVAAVTRWSGARTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAADSTNRNSGAVYYSWAYDYWGQGTQVTVSS 192F2 12EVQLVESGGGLVQAGGSLRLSCEASGRTFSPIAMGWFRQAPGKEREFVAVVTRWSGARTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAADSTNRNSGAIYYTWAYDYWGQGTQVTVSS

TABLE A-2 F-protein sequences SEQ ID F-protein NO: Sequence RSV LONG 17MELPILKANAITTILAAVTFCFASSQNITEEFYQSTCSAVSKG M-2YLSALRIGWYTSVITIELSNIKENKCNGTDAKVKLIKQELDKYKNAVTFLQLLMQSTFAANNRARRELPRFMNYTLNNTKKTNVTLSKKRKRRFLGFLLGVGSATASGTAVSKVLHLEGEVNKIKSALLSINKAVVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCRISNIETVIEFQQKNNRLLEITREFSVNAGVTTPVSTYMLTNSELLSLINDMPITNDQKKLMSNNVQIVRQQSYSIMSIIKEEVLAYVVQLPLYGVIDTPCWKLHTSPLCTTNTKEGSNICLTRTDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNLCNVDIFNPKYDCHIMTSKTDVSSSVITSLGAIVSCYGKTKCTASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSZYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLHHVNAGKSTTNIMITTIIIVIIVILLSLIAVGLLLYCKARSTPVTL SKDQLSGINNIAFSN RSV A-2 118MELLILKANAITTILTAVTFCFASGQNITEEFYQSICSAVSKGYLSALRTGWYTSVITIELSNIKHNKONGTDAKVKLIKQELDKYKNAVTELTLLMQSTQATNNRARRELPRFMNYTLNNAKKTNVILSNKRKRRFLGFLLGVGSATASGVAVSKVLHLEGEVNKIKSALLSTNKAVVSLSNGVSVLTSKVLDLKNYIDKQLLPIVNKQSCSISNIETVIEFQQKNNRLLEITREFSVNAGVITPVSTYMLINSELLSLINDMPITNDQKKLMSNNVQIVRQQSYSTMSIIKEEVLAYVVQLPLYGVIDTPOWKLHISPLOTTNTKEGSNICLTRIDRGWYCDNAGSVSFFPQAETCKVQSNRVFCDTMNSLTLPSEVNLONVDIFNPKYDCKIMISKTDVSSSVITSLGAIVSCYGKTKCIASNKNRGIIKTFSNGCDYVSNKGVDTVSVGNTLYYVNKQEGKSLYVKGEPIINFYDPLVFPSDEFDASISQVNEKINQSLAFIRKSDELLHNVNAGKSTTNIMITTIIIVIIVILLSLTAVGLLLYCKARSTPVTL SKDQLSGINNIAFSN RSV B-1  19MELLIHRSSAIFLTLAVNALYLISSQNITEEFYQSTCSAVSRGYFSALRIGWYTSVITIELSNIKETKCNGTDTKVKLIKQELDKYKNAVIELQLLMQNTPAANNRARREAPQYMNYTINTYKNLNVSISKKRKRRFLGFLLGVGSAILSGIAVSKVLHLEGEVNKTKNALLSTNKAVVSLSNGVSVLTSKVLDLKNYINNALLPIVNQQSCRISNIETVIEFQQMNSRLLEITREFSVNAGVTTPLSTYMLTNSELLSLINDMPITNDOKKLMSSNVQIVRQQSYSIMSIIKEEVLAYVVQLPIYGVIDTPCWKLHISPLCTTNIKEGSNICLIRTDRGWYCDNAGSVSFFPQADTCKVQSNRVFCDTMNSLILPSEVSLONTDIFNSKYDCKIMTSKTDISSSVITSLGAIVSCYGKIKCIASNKNRGIIKTFSNGCDYVSKKGVDTVSVGNTLYYVNKLEGKNLYVKGEPIINYYDPLVEPSDEFDASISQVNEKINQSLAFIRRSDELLHNVNTGKSTINTMITTIIIVIIVVLLLLIAIGLLLYCKAKNTPVTLSNDQLSGINNTAF SK

TABLE A-3 Amino add sequences of multivalent constructs that bind hRSVSEQ ID Construct NO: Sequence RSV101 20EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSG AYYYAWAYDYWGQGTQVTVSSRSV102 21 EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSS RSV103 22EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGOGGSGGGGSGGGGSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMSWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVTLQMNSLKPEDTAVYTCAAELTNRNSGAYYYRWAYDYWGQGTQVTVSS RSV104 23EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAW AYDYWGQCTQVTVSSRSV105 24 EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAY DYWGQGTQVTVSS RSV10625 EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSY IYIWAYDYWGQGTQVTVSSRSV107 26 EVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDY WGRGTQVTVSS RSV108 27EVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIY DWSYDYWGRGTQVTVSSRSV109 28 EVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSFIYDWAYDHWGQGTQVTVSSGGGGSGGGSEVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSFIYDWAY DHWGQGTQVTVSS RSV11029 EVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSFIYDWAYDHWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSF IYDWAYDHWGQGTQVTVSSRSV113 30 EVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSY YPRYDYWGQGTQVTVSSRSV114 31 EVQLVESGGGWVQAGGSLRLSCAASGRAFSSYAMGWIRQAPGKEREFVAGIDQSGESTAYGASASGRFIISRDNAKNTVHLLMNSLQSDDTAVYYCVADGVLATTLNWDYWGQGTQVTVSSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGWVQAGGSLRLSCAASGRAFSSYAMGWIRQAPGKEREFVAGIDQSGESTAYGASASGRFIISRDNAKNTVHLLMNSLQSDDTAVYYCVADGVLATTLNWD YWGQGTQVTVSS RSV11532 EVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSSGGGGSGGGGSGGGGGGGSEVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSS RSV116 33EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQLVESCGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIY DWSYDYWGRGTQVTVSSRSV201 34 EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERS YDYWGQGTQVTVSS RSV20235 EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSD SLSERSYDYWGQGTQVTVSSRSV203 36 EVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWERQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSS RSV204 37EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGREREFVAAISWSDGSTYYRDSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQRGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAENTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYI YDWSYDYWGRGTQVTVSSRSV205 38 EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSS RSV206 39EVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSS RSV207 40EVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSINPGSYIYIWAYDYWGOGTQVTVSS RSV301 41EVQLVESGGGINQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSS RSV302 42EVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSS RSV303 43EVQLVESGGGLVQAGGSLRLSCAASGPTFSADTMGWFRQAPGKEREFVATIPWSGGIAYYSDSVKGRFTMSRDNAKNTVDLQMNSLKPEDTALYYCAGSSRIYIYSDSLSERSYDYWGQGTQVTVSSGGGGSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSS RSV305 44EVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSSGGGCSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVIVSS RSV306 45EVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS RSV400 46EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGOSLRLSCAASGETESSYANGWFRQAPGKEREFVAASWSDGSTYILDSVKGRFTISRDNPLKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTESSYAMGWFRQAPGKEREFVAATSWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSS RSV401 47EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGETAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSS RSV402 48EVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSS RSV403 49EVQLVESGGGLVQAGDSLRLSCAASGRTFSSYAMGWFRQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWERQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGOYSGSYYPRYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGDSLRLSCAASGRTESSYAMGWERQAPGKEREFVAAISWSDGSTYYADSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCAADLTSTNPGSYIYIWAYDYWGQGTQVTVSS RSV404 50EVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGCSEVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCAASGRSFSNYVLGWFRQAPGKEREFVAAISFRGDSAIGAPSVEGRFTISRDNAKNTGYLQMNSLVPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS RSV405 51EVQLVESGGGLVQAGGSLRISCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLRLSCEASGRTYSRYGMGWFRQAPGKEREFVAAVSRLSGPRTVYADSVKGRFTISRDNAENTVYLQMNSLKPEDTAVYTCAAELTNRNSGAYYYAWAYDYWGQGTQVTVSS RSV406 52EVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSFIYDWAYDHWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGRTFSSIAMGWFRQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPEDTAVYYCAVDTASWNSGSFIYDWAYDHWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCARSGRTFSSIAMGWERQAPGKEREFVAAISWSRGRTFYADSVKGRFIISRDDAANTAYLQMNSLKPFDTAVYYCAVDTASWNSGSFIYDWAYDHWGQGTQVTVSS RSV407 53EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTFLNPGAYIYDWSYDYWCRGTQVTVSSGGSGSGGGGSGGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAFDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGCGSGGGGSGGGGSFVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS RSV408 54EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGFPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSAAAEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS RSV409 55EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVEGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVRAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYTYDWSYD YWGRGTQVTVSS RSV410 56EVQLVESGGGIVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLCWFRQAPGKEREFVAAINWRCDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRETISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS RSV411 57EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYTYDWSYDYWGRGTQVTVSSGGGGSGGGGSGOGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYTIDWSYDYWGRGTQVTVSSGGGSSGSGGSGGGGSEVQLVESGGCLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQ GTQVTVSS RSV412 58EVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAADPALGCYSGSYYPRYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGCSGGGGSGGGGSEVQLVESSGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGR GTQVTVSS RSV413 59EVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGLTLDYYALGWFRQAPGKEREGVSCISSSDHSTTYTDSVKGRFTISWDNAKNTLYLQMNSLKPGDTAVYYCAALPALGCYSGSYYPRYDYWGQGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGR GTQVTVSS

TABLE A-4 Sequences of humanized and/or sequence optimized NC41 variantsSEQ Nanobody ® ID Sequence NC41v01  60EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTLYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v02  61EVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLAFEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v03  62EVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLAPEDTAVYYCGAGTPLNPGAYTYDWSYDYWGQGTLVTVSS NC41v04  63EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPDDTAVYYCGAGTPLNPGAYTYDWSYDYNGQGTLVTVSS NC41v05  64EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQCTLVTVSS NC41v06  65EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTLVYYGGAGTPLNPGAYIYDWSYDYNGQGTLVTVSS NC41v07  66EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTLYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWCQGTLVTVSS NC41v08  67EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v09  68EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRCDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v10  69EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGFPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC47v11  70EVQLLESGGCLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTINTVSS NC41v17  71EVQLLESGGGLVQPGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v13  72EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPEDTAVYYCGAGTPLNPCAYIYDWSYDYWGQGTLVTVSS NC41v14  73EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v15  74EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTLYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v17  75EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v16  76EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v19 146EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWCQGTLVTVSS NC41v20 147EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGFPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWCQGTLVTVSS NC41v21 148EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v22 149EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v23 150EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTINTVSS NC41v24 151EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLOMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSS NC41v25 152EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSS NC41v26 153EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTCYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSS NC41 E1D 138DVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVLAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTQVTVSS NC41v03 E1D 139DVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v06 315 140DVQLLESGGGLVUGGSLRLSCAASGGSLSNYVLGWFRQAPGKGRETFAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v18 315 141DVQLLESGGGLVOGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGFPNVEGRFTISRDNSKNTLYLWNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v17 ElD 154DVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRETISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v21 E1D 155DVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGFPNVEGRFTISRDNAKNTGYLQMNSLAPEDTAVYYCGAGTPLNPGAYIYDWSYDYTGQGTLVTVSS NC41v22 E1D 156DVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS NC41v26 315 157DVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGATIYDWSYDYWGRGIIVTVSS

TABLE A-5 Amino acid sequence of multivalent humanized and/orsequence optimized constructs that bind hRSV SEQ ID Nanobody ® NOSequence RSV414  77 EVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQPPGNGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGSGGSGGGSSEVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLSWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGCSEVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV426  78EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYTYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGSGSEVTLLESGGGLVQPGGSLRLSORRSSCSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV427  79EVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGSSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLSWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV442 158EVQLLESGGGLVQPGGSLRLSCARSGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRFEDTAVYYCGACTPLNPGAYTYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLWINSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSZVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLSWFRQAPGKGREEVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGASTPLNPGAYIYOWSYDYWGQGTLVTVSS RSV436 159EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSSGGCSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV438 160EVQLVESGSGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYTYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKERETVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV439 161EVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGINQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAHNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSS RSV434 142DVQLVESGGCLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDTTIGFPNVEGRFTISRDNAKNTGYLOMNSLAEDDTAVYYCGAGTPLNPGAYIYDWSYDYWGRCTQVTVSSGGGGSGGGGSOGGCSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGHEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLWINSLAPDDTAVYYCGAGTPLNPGAYIYDWSYDYWORGTQVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQAGGSLSISCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLAPDDTAVYYCGAGTPLNPGLYIYDWSYDYWGRGTQVTVSS RSV443 143DVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTLVYYCGAGTPLNPGAYTYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRISCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTTNTVSS RSV444 144DVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGCSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVRAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYTYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNAKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV445 145DVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTTSRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGCSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRDDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV435 162DVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGHGREFVAAINWRGDITTGPPNVEGRFTISRDNSNNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQCTLVTVSSGGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITIGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTPNYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSOGGGSGGGGSGGGGSEVQLLESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKGREFVAAINWRGDITTGPPNVEGRFTISRDNSKNTLYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV437 163DVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPDDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV441 164DVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGREREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSSOGGGSGGGGSGGGGSEVQLVESGGGIVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGQGTLVTVSS RSV440 165DVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSSGGGGSGGGSSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRITISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSSGGGGSGGGGSGGGGSEVQLVESGGGLVQPGGSLRLSCAASGGSLSNYVLGWFRQAPGKEREFVAAINWRGDITIGPPNVEGRFTISRDNAKNTGYLQMNSLRPEDTAVYYCGAGTPLNPGAYIYDWSYDYWGRGTLVTVSS

TABLE A-6 Preferred combinations of CDR sequences Nano- SEQ SEQ SEQ SEQbody ® ID FR1 ID CDR 1 ID FR2 ID CDR 2 NC41   5 EVQLVESGGGLVQAGG  80NYVLG 98 WERQAPG  99 ATNWRGDITI SLSISCAASGGSLS KEREFvA GPPNVEG NC41v01 60 evqllesggglvgpgg  81 NYVLG 98 wfrqapg 100 AINWRGDITI slrlscaasggslskgrefva GPPNVEG NC41v02  61 evqllesggglvqpgg  82 NYVLG 98 wfrqapg 100AINWRGDITI slriscaasggsls kgrefva GPPNVEG NC41v03  62 evqllesqgqlvqpgg 83 NYVLG 98 wfrqapg 100 AINWRGDITI slriscaasggsls kgrefva GPPNVEGNC41v04  63 evqllesggglvgpgg  84 NYVLG 98 wfrqapg 100 AINWRGDITIslsiscaasggsls kgrefva GPPNVEG NC41v05  64 evqllesggglvqpgg  85 NYVLG 98wfrgapg 100 AINWRGDITI slsiscaasggsls kgrefva GPPNVEG NC41v06  65evgllesggglvqpgg  86 NYVLG 98 wfrqapg 100 AINWRDDITI slrlscaasggslskgrefva GPPNVEG NC41v07  66 evqllesggglvqpgg  87 NYVLG 98 wfrqapg 100AINWRGNITI slsiscaasggsls kgretva GPPNVEG NC41v08  67 evqllesggglvqpgg 88 NYVLG 98 wfrqapg 100 AINWRGDITI slsiscaasggsls kgrefva GPPNVEGNC41v09  68 evqllesggglvqpgg  89 NYVLG 98 wfrqapg 100 AINWRGDITIslsiscaasggsls kgrefva GPPNVEG WC41v10  69 evqllesgqglvqpgg  90 NYVLG 98wfrqapg 100 AINWRGDITI slsiscaasggsls kgrefva GPPNVEG NC41v11  70evq1lesqggavgagg  91 NYVLG 98 wfrgapg 100 AINWRGDITT slsiscaasggslskgrefva GPPNVEG NC41v12  71 evqllesggglvqpgg  92 NYVLG 98 wfrqapg  99AINWRGDITT slsiscaasggsls kgrefva GPPNVEG NC41v13  72 evqllesggglvqpgg 93 NYVLG 98 wfrqapg 100 AINWRGDIT1 slrlscaasggsls kgrefva GPPNVEGNC41v14  73 evqllesggglvqpgg  94 NYVLG 98 wfrqapg 100 AINWRGDITTslrlscaasggsls kgrefva GPPNVEG NC41v15  74 evq1lesgqglvgagg  95 NYVLG 98wfrgapg 100 AINWRGDITT slrlscaasggsls kgrefva GPPNVEG NC41v17  75evgllesggglvqpgg  96 NYVLG 98 wfrqapg 100 AINWRGDITT slrlscaasggslskgrefva GPPNVEG NC41v18  76 evqllesggglvqpgg  97 NYVLG 98 wfrqapg 100AINWRDDITI slrlscaasggsls kgrefva GPPNVEG NC41v19 146 EVQLVESGGGLVQPGG166 NYVLG 98 WFRQAPG  99 AINWRGDITI SLRLSCAASGGSLS KEREFVA GPPNVEGNC41v20 147 EVQINESGGGLVQPGG 166 NYVLG 98 WFRQAPG  99 AINWRGDITISLRLSCAASGGSLS KEREFVA GPPNVEG NC41v21 148 EVQLVESGGGLVQPGG 166 NYVLG 98WFPQAPG  99 AINWRGDITI SLRLSCAASGGSLS NEREDIA GPPNVEG NC41v22 149EVQLVESGGGLVQPGG 166 NYVLG 98 WFRQAPG  99 AINWRGDITI SLRLSCAASCGSLSKEREFVA GPPNVEG NC41v23 150 EVQLVESGGGLVQPGG 166 NYVLG 98 WFRQAPG  99AINPRGDITI SLRLSCAASGGSLS KEREFVA GPPNVEG NC41v24 151 EVQLVESGGGLVQPGG166 NYVLG 98 WFRQAPG  99 AINWRGDITI SLRLSCAASGGSLS NEREFVA GPPNVEGNC41v25 152 EVQLVESGGGLVQPGG 166 NYVLG 98 WFRQAPG  99 AINWRGDITISLRLSCAASGGSLS NEREEVA GPPNVEG NC41v26 153 EVQLVESGGGLVQPGG 166 NYVLG 98WFRQAPG  99 AINWRGDITI SLRLSCAASGGSLS KEREFVA GPPNVEG Nano- SEQ SEQ SEQSEQ body ® ID FR3 ID CDR 3 ID FR4 ID NC41 101 RFTISRDNAKNTGYLQ 103GTPLNPGAYI 121 WGRGTDVTVSS 122 MNSLAPDDTAVYYCGA YDWSYDY NC41v01 101rftisrdnakntlylq 104 GTPLNPGAYI 121 wgggtlvtvss 123 mnslapedtavyycgaYDWSYDY NC41v02 101 rftisrdnskntlylq 105 GTPLNPGAYI 121 wgqgtlvtvss 123mnslapedtavyycga YDWSYDY NC41v03 101 rftisrdnskntlyiq 106 GTPLNPGAYI 121wgqgtlvtvss 123 mpslrpedtavyycga YDWSYDY NC41v04 101 rftisrdnskntlylq107 GTPLNPGAYI 121 wgqgtlvtvss 123 mnslrpddtavyycga YDWSYDY NC41v05 101rftisrdnskntlylq 108 GTPLNPGAYI 121 wgqgtlvtvss 123 mnslapedtavyycgaYDWSYDY NC41v06 102 rftisrdnakntlylq 109 GTPLNPGAYI 121 wgqgtlvtvss 123mnsirpedtavyycga YDWSYDY NC41v07 101 rftisrdnakntlylq 110 GTPLNPGAYI 121wgggtlvtvss 123 mnslapddtavyycga YDWSYDY NC41v08 101 rftisrdnakntlylq111 GTPLNPGAYI 121 wgqgtlvtvss 123 mnslrpedtavyycga YDWSYDY NC41v09 10rftisrdnskntlylq 112 GTPLNPGAYI 121 wgqgtlvtvss 123 mnslrpddtavyycgaYDWSYDY WC41v10 101 rftisrdnakntgylq 113 GTPLNPGAYI 121 wgqgtlvtvss 123mnslapddtavyycga YDWSYDY NC41v11 101 rftisrdnakntgylq 114 GTPLNPGAYI 121wgqgtlvtvss 123 mnslapddtavyycga YDWSYDY NC41v12 101 rftisrdnakntgylq115 GTPLPPGAYT 121 wgqgtlvtvss 123 mnslapddtavyycga YDWSYDY NC41v13 101rftisrdnakntgylq 116 GTPLNPGAYI 121 wgqgtlvtvss 123 mnslapedtavyycgaYDWSYDY 8C41v14 101 rftisrdnskntlylq 117 GTPENPGAYI 121 wgqgtlvtvss 123mnslapedtavyycga YDWSYDY NC41v15 101 rftisrdnakntlylq 118 GTPLNPGAYI 121wgggtlvtvss 123 mnslapedtavyycga YDWSYDY NC41v17 101 rftisrdnskntlylq119 GTPLNPGAYI 121 wgggtlvtvss 123 mnslrpedtavyycga YDWSYDY NC41v18 102rftisrdnskntlylq 120 GTPLNPGAYI 121 wgqgtlvtvss 123 mnslrpedtavyycgaYDWSYDY NC41v19 101 RFTISPDNAKETGYLQ 103 GTPLNPGAYI 121 WGQGTLVTVSS 123MNSLAPDDTAVYYCGA YDWSYDY NC41v20 101 RFTISRDNAKNTGYLQ 167 GTPIMPGAYI 121WGQGTLVTVSS 123 MNSLRPDDTAVYYCGA YDWSYDY NC41v21 101 RFTISRDNAKNTGYLQ116 GTPLNPGAYI 121 WGQGTLVTVSS 123 MNSLAPEDTAVYYCGA YDWSYDY NC41v22 101RFTISPDNAKNTGYLQ 166 GTPLNPGAYI 121 WGQGTLVTVSS 123 MNSLRPEDTAVYYCGAYDWSYDY NC41v23 101 RFTISPDNAKNTGYLQ 103 GTPLNPGAYI 121 WGRGTLVTVSS 169MNSLAPDDTAVYYCGA YDWSYDY NC41v24 101 RFTISRDNAKNTGYLQ 167 GTPLNPGAYI 121WGRGTLVTVSS 169 MNSLPPDDTAVYYCGA YDWSYDY NC41v25 101 RFTISRDNAKNTGYLQ116 GTPLNPGAYI 121 WGRGTLVTVSS 169 MNSLAPEDTAVYYCGA YDWSYDY NC41v26 101RFTISPDNAKNTGYLQ 168 GTPLNPGAYI 121 WGRGTLVTVSS 169 MNSLRPEDTAVYYCGAYDWSYDY

TABLE A-7 Linker sequences Linker SEQ ID NO: Sequences SGS 124 GGGGS 7GS125 SGGSGGS 9GS 126 GGGGSGGGS 10GS 127 GGGGSGGGGS 15GS 128GGGGSGGGGSGGGGS 18GS 129 GGGGSGGGGSGGGGGGGS 20GS 130GGGGSGGGGSGGGGSGGGGS 25GS 131 GGGGSGGGGSGGGGSGGGGSGGGGS 30GS 132GGGGSGGGGSGGGGSGGGGSGGGGSGGGGS 35GS 133GGGGSGGGGSGGGGSGGGGSGGGGSGGGGSGGGCS G1 hinge 134 EPKSCDKTHTCPPCP 9GS-G1135 GGGGSGGGSEPKSCDKTHTCPPCP hinge G3 hinge 136ELKTPLGDTTHTCPRCPEPKSCDTPPPCPRCPEPKSCDTPPPCPRCP EPKSCDTPPPCPRCP 3Ala 137AAA

TABLE B-1 Characteristics of Nanobodies ® that bind hRSV F-proteinCompetition Binding Synagis ® RSV neutralization hRSV Fab kineticanalysis IC50 (nM)(n = 2) Clone Family Epitope EC50 EC50 ka (1/Ms) kd(1/s) KD Long A-2 B1 191D3 LG 3sub2 II 1.5E−10 5.9E−09 1.5E+06 2.8E−031.9E−09 253 227 — 1E4 LG 3sub2 II 6.6E−11 4.5E−09 8.0E+05 1.3E−031.6E−09 380 298 ND 7B2 16 II 9.0E−11 1.9E−09 5.7E+05 6.5E−04 1.1E−09 91177 2690 NC23 34 II 1.0E−10 2.3E−09 8.0E+05 7.4E−04 9.2E−10 144 109 —15H8 29 II 8.3E−10 3.9E−08 1.2E+06 2.1E−02 1.6E−08 200 218 2340 NC41 29II 4.1E−10 3.2E−08 8.2E+05 6.7E−03 8.1E−09 58 26 4000 15B3 4sub1 IV-VI5.8E−11 — 4.1E+05 2.7E−04 6.7E−10 — — 1274 191E4 LG 21 IV-VI 8.3E−11 —5.7E+05 1.5E−04 2.7E−10 — — 4327 Synagis ® II 2.8E+05 1.8E−04 6.4E−10 42.5    1.7

TABLE B-2 Nomenclature for multivalent Nanobody ® constructs directedagainst hRSV F-protein Type Name Construct SEQ ID NO Bivalent RSV101191D3-15GS-191D3 20 RSV102 191D3-25GS-191D3 21 RSV103 191D3-35GS-191D322 RSV104 191D3-9GS-191D3 23 RSV105 7B2-9GS-7B2 24 RSV106 7B2-15GS-7B225 RSV107 15H8-9GS-15H8 26 RSV108 15H8-15GS-15H8 27 RSV109 NC23-9GS-NC2328 RSV110 NC23-15GS-NC23 29 RSV113 15B3-15GS-15B3 30 RSV114NC39-20GS-NC39 31 RSV115 191E4-18GS-191E4 32 RSV116 NC41-15GS-NC41 33Biparatope RSV201 191D3-9GS-191E4 34 RSV202 191D3-15GS-191E4 35 RSV203191D3-25GS-191E4 36 RSV204 7B2-15GS-15H8 37 RSV205 7B2-15GS-15B3 38RSV206 15H8-15GS-15B3 39 RSV207 15H8-15GS-7B2 40 RSV301 191E4-9GS-191D341 RSV302 191E4-15GS-191D3 42 RSV303 191E4-25GS-191D3 43 RSV30515B3-15GS-7B2 44 RSV306 15B3-15GS-15H8 45 Trivalent RSV4007B2-15GS-7B2-15GS-7B2 46 RSV401 7B2-15GS-7B2-15GS-15B3 47 RSV40215B3-15GS-7B2-15GS-7B2 48 RSV403 7B2-15GS-15B3-15GS-7B2 49 RSV40415H8-15GS-15H8-15GS-15H8 50 RSV405 191D3-15GS-191D3-15GS-191D3 51 RSV406NC23-15GS-NC23-15GS-NC23 52 RSV407 NC41-15GS-NC41-15GS-NC41 53 RSV408NC41-AAA-NC41-AAA-NC41 54 RSV409 NC41-9GS-NC41-9GS-NC41 55 RSV410NC41-20GS-NC41-20GS-NC41 56 RSV411 NC41-15GS-NC41-15GS-15B3 57 RSV41215B3-15GS-NC41-15GS-NC41 58 RSV413 NC41-15GS-15B3-15GS-NC41 59

TABLE B-3 Reactivity of monovalent Nanbodies® with antigen extracts ofHEp-2 cells infected with different escape mutants of the Long strain

TABLE B-4 Reactivity of monovalent and bivalent Nanobodies® with antigenextracts of HEp-2 cells infected with different escape mutants of theLong strain

TABLE B-5 Neutralization and kinetic binding parameters in Biacore onF_(tm)-NN protein for selected NC41 variants Neutralization IC50 (nM)Biacore (F_(tm-)NN) Name Long B-1 Long B-1 ka (1/Ms) kd (1/s) KD (M)NC41 202 4707 122 3291 1.7E+06 6.70E−03 4.00E−09 NC41v03 255 1507 nd ndnd nd nd NC41v06 111 806 nd nd 2.0E+06 4.80E−03 2.50E−09 NC41v17 249 677149 346 1.9E+06 5.90E−03 3.20E−09 NC41v18 116 728 98 194 nd nd ndSynagis 7.3 2.1 6.0 2.9

TABLE B-6 Trivalent humanized and/or sequence optimized variants of NC41Name Construct SEQ ID NO RSV414 NC41v03-15GS-NC41v03-15GS-NC41v03 77RSV426 NC41v06-15GS-NC41v06-15GS-NC41v06 78 RSV427NC41v18-15GS-NC41v18-15GS-NC41v18 79 RSV434NC41^(E1D)-15GS-NC41-15GS-NC41 142 RSV435NC41v17^(E1D)-15GS-NC41v17-15GS-NC41v17 162 RSV436NC41v20-15GS-NC41v20-15GS-NC41v20 159 RSV437NC41v20^(E1D)-15GS-NC41v20-15GS-NC41v20 163 RSV438NC41v22-15GS-NC41v22-15GS-NC41v22 160 RSV439NC41v26-15GS-NC41v26-15GS-NC41v26 161 RSV440NC41v26^(E1D)-15GS-NC41v26-15GS-NC41v26 165 RSV441NC41v22^(E1D)-15GS-NC41v22-15GS-NC41v22 164 RSV442NC41v17-15GS-NC41v17-15GS-NC41v17 158 RSV443NC41v03^(E1D)-15GS-NC41v03-15GS-NC41v03 143 RSV444NC41v06^(E1D)-15GS-NC41v06-15GS-NC41v06 144 RSV445NC41v18^(E1D)-15GS-NC41v18-15GS-NC41v18 145

TABLE B-7 Neutralization of Long and B-1 by trivalent NC41 variants LongB-1 Ratio Ratio to ID Trivalent IC50 [M] to Synagis IC50 [M] SynagisExperimental Series 1 RSV407 NC41 9.41E−11 59  6.6E−10 3 RSV414 NC41v037.81E−11 72 1.61E−10 11 RSV426 NC41v06 8.98E−11 63 9.32E−11 20 RSV427NC41v18 9.13E−11 62 4.61E−11 40 Experimental Series 2 RSV407 NC4113.06E−11  111   51E−11 11 RSV434 NC41 (E1D)   15E−11 107   56E−11 9RSV441 NC41v22 7.94^(E)−11 209 (E1D)

TABLE B-8 Neutralization capacity of RSV434 and Synagis in plaque assayagainst various clinical isolates Comparison Comparison Number with100-fold between Number with complete virus between RSV reduction orgreater (%) study drugs inhibition (%) study drugs group Synagis RSV434P value Synagis RSV434 P value RSV/A 27/31 (87.1%) 31/31 (100%)  0.11 1/31 (3.2%) 29/31 (93.5%) <0.0001 RSV/B 26/30 (86.7%) 28/30 (93.3%)0.67 11/30 (36.7%) 22/30 (73.3%) 0.009 Total 53/61 (86.9%) 59/61 (96.7%)0.09 12/61 (19.7) 51/61 (83.6%) <0.0001

TABLE B-9 Overview table of all cotton rat experiments performed showingboth the detection of replication competent virus and viral RNA at day 4post inoculation (in experiment 3 detection at day 7 was also performed)Viral load difference Fold versus reduction control viral Nanobody(log₁₀ RNA dose Treatment regimen pfu) (2^(ΔCT)) Exp 1 RSV407   5 mg/kgProphylactic day −1 −2.59* 286.7*  Therapeutic day +1, 2, +3 −2.88* 4.4* Therapeutic day +2, +3 −2.83*  4.6* Exp 2 RSV407   5 mg/kgProphylactic day −1 −3.01* 79.2*   1 mg/kg −2.37* 61.3*  0.2 mg/kg−1.43* 28.1* 0.04 mg/kg −0.37 11.7* Exp 3 RSV407   5 mg/kg Therapeuticday +1 −2.04*  2.9* (Read out at day 7) (0.63*) (1.8) Therapeutic day+1, +2 −2.47*  2.5* (Read out at day 7) (0.57)  (4.5*) Exp 4 RVS407  0.2mg/kg Prophylactic day −1 −0.75* 29.8* RSV503   1 mg/kg −1.27* 31.4* 0.2 mg/kg −0.71* 30.4* 0.04 mg/kg −0.22* 15.5* Exp 5 RSV434   20 mg/kgTherapeutic day +2, +3 −2.89* 10.2*   4 mg/kg −1.76* 1.9   2 mg/kg−1.81*  5.5*   1 mg/kg −1.66*  3.9* Exp 6 RSV434   5 mg/ml Therapeuticday +2, +3 −3.15* 10*     20 mg/ml −2.64*  2.4*   80 mg/ml −3.30*  4.3**p < 0.05

The invention claimed is:
 1. A polypeptide consisting of an amino acidsequence comprising or consisting of SEQ ID NO:142.
 2. A composition,comprising the polypeptide according to claim
 1. 3. The compositionaccording to claim 2, wherein the composition is a pharmaceuticalcomposition.
 4. The pharmaceutical composition according to claim 3,wherein the pharmaceutical composition comprises a carrier suitable forpulmonary delivery.
 5. A method for the treatment of hRSV infection,said method comprising administering to a subject in need thereof apharmaceutically effective amount of the polypeptide according toclaim
 1. 6. The method of claim 5, wherein the hRSV infection is a lowerrespiratory tract infection.
 7. A pharmaceutical device suitable for thepulmonary delivery of a polypeptide, wherein the pharmaceutical devicecomprises the polypeptide according to claim
 1. 8. The pharmaceuticaldevice according to claim 7, wherein the pharmaceutical device is anebulizer.